The man at the other end of line has a profile picture of a cute laughing baby on his cellphone profile and says he wants to become the number one assassin of ISIS commanders.

Omar, not his real name, is waging a ferocious and very personal battle with the extremist group that has occupied his native city, Al-Raqqa, in Syria.

He is fighting on two fronts: directly in battles with the local brigades that are taking on both ISIS and the Assad regime; and as a human trafficker, helping ISIS defectors escape the Islamic State.

Omar is part of a new Syrian resistance to the year-long ISIS invasion — a resistance movement that uses the same porous border between Turkey and Syria that smugglers also use to bring in new ISIS recruits to carry ISIS defectors in the other direction.

CBC News was introduced to Omar through the Al-Raqqa Revolutionary Brigade, which is part of the Free Syrian Army in northern Syria, a principal conduit for those who want to escape ISIS. We then had a series of calls with Omar for over a month to learn more about him and to establish his bona fides.

By his account, he is in his early 30s, not yet married, though the subject often enters his mind during the tense cat-and-mouse existence he leads. "I am not sure I will live long enough to get married before the bullet that has been stuck in my stomach kills me."

His story is not uncommon. In the past two years, he fought with one of the local brigades in northern Syria against different armed groups, including the Syrian regime, Syrian militias and ISIS.

He said he was the target of an assassination attempt — hence the bullet he says is still lodged in his stomach. At that point, he decided to fake his own death and live under an assumed name.

Hatred of ISIS

The reason for his hatred of ISIS is simple: "They claimed to be friends to the Syrian people," Omar told CBC News by Skype, connecting from an undisclosed location.

"But after establishing their state, they either killed who opposed them, or called them apostate."

These days, Omar is busy with his own cell, or brigade of 18, fighters of both genders who share his views on ISIS.

He claims that his group has so far helped 20 ISIS foreign defectors to escape, including one young Canadian man who made his getaway a few months back.

He also told CBC News he has a waiting list of ISIS members who want to escape. But the journey is a treacherous one across mountainous terrain, never knowing where an enemy might exist, until they reach freedom in Turkey.

Syrians who had fled Tel Abyad, a city about an hour north of Al-Raqqa, prepare to return home from Turkey last month after the Kurdish People's Protection Units retook the town from ISIS. (Rodi Said / Reuters)

Last month, one member of Omar's cell was executed by ISIS and he tries to console himself by saying this is war.

His group is using its own money, Omar says, for disguises, bribes, fueling vehicles and other expenses.

And it is taking these risks for different reasons, not least of which, says Omar, is so that defectors can raise awareness about the evils of ISIS.

The back and forth migration

Foreign fighters who join ISIS can become disillusioned for a variety of reasons, it seems.

CBC News talked to different local sources in addition to the Al-Raqqa Revolutionary Brigade to inquire about the smuggling process and the reasons behind the defections.

ARB media officer Abdelrahman Alsaleh claimed that most of the escapees run away because they weren't finding the utopia they were seeking, and that some ISIS recruits apparently feel the group is not implementing the real Islam. Rather, that it is using Islam to further its quest for power.

Other factors include the U.S.-led airstrikes, the battles with Syrians, Iraqis and other armed groups, the strict lifestyle ISIS members must adhere to and the fatwas that ISIS has imposed inside the Islamic State.

When defectors decide to leave, they often use their contacts back home — either friends or relatives — to try to arrange an escape plan.

But the intelligence wing of ARB is the most direct source for fighters to escape ISIS, Alsaleh claimed.

Members of the ARB intelligence group are originally from the city of Al-Raqqa in north-central Syria and claim that their local knowledge gives them an advantage over ISIS as a large portion of ISIS leaders were neither born in nor grew up in northern Syria.

The photo is said to be of a French woman and her son who escaped ISIS with the assistance of the ARB. The woman is holding a paper that says “Thank you Al-Raqqa Revolutionaries Brigade, you saved me from ISIS.” (Photo supplied by Al-Raqqa Revolutionary Brigade)

Spying and smuggling

Abu Bakker, is the nom de guerre of a Syrian smuggling strategist who has also dedicated himself to fighting ISIS.

He told CBC News that he recently helped three men to escape ISIS, two of whom were from Europe.

In contrast to Omar's group, Abu Bakker does not take responsibility for delivering the defectors to Turkey.

"My responsibility," he said, "is to take them out of ISIS-controlled areas only."

Abu Bakker, who pays his smuggling expenses by freelance writing, says his main goal in risking his life is to get the best weapon to defeat ISIS — intelligence about the Islamic State.

Abu Bakker believes that ISIS is penetrated by the world's intelligence apparatuses, and he, too, was once a spy inside ISIS.

He lived among ISIS leaders until he was awarded a high position in their state. He ran away because, he said, he knew he would look suspicious if he refused the offer.

He still has contacts, he says, within Islamic State, but when asked if he can trust the people he deals with in the murky world of spying and defectors, he says there is no way to check the credibility of those asking to flee ISIS apart from "hunches".

"I coordinate with everybody who is willing to work against ISIS," he says, noting the work of Syrian rebels in connecting him with defectors. "Syrian rebels play a very big role."

A religious Muslim, Abu Bakker says "ISIS uses the name of Islam in a bad way," and so he considers his war against them a personal jihad.

ISIS is clearly feeling pressure to stop defectors — by keeping recruits' passports and putting restrictions on travel outside the IS-controlled territories. But Syrian activists believe that hundreds of ISIS members are looking for ways to run away.