The founders of TransferWise, getting naked on the streets of London to challenge the banks. TransferWise TransferWise is known for its provocative publicity stunts — particularly those involving nudity.

In January 2015, the Estonian money transfer app sent a dozen nearly naked employees running through London to protest banks' "unfair exchange rates." It was at it again in February, leading a 200-strong underwear-only march through Wall Street in New York to celebrate their launch in the US.

Even the founders have had a go: Back in June 2014, Taavet Hinrikus and Kristo Käärmann stripped down to their underpants along with dozens of employees in the City of London to illustrate how, they said, the banks “screw you by charging huge hidden charges.”

But TransferWise is less keen on risqué activities when they're not helping to promote the company.

Dimo Trifonov is the founder and CEO of 3nder, an alternative dating app. It focuses on polyamory, kink, and alternative sexual preferences, describing itself as a "way to date awesome people around you who are kinky, curious and open-minded." (It has also been described as "Tinder for threesomes.") It has 650,000 users — 70,000 of which are in the UK, where Trifonov is based — and handles 3 million messages a month.

However, 3nder's unconventional audience has caused problems for Trifonov, both in his professional and personal life.

TransferWise refused to let the company open a business account because of the "nature of [his] business," according to an email seen by Business Insider, with a customer-service representative classifying the dating app as "adult" content, Trifonov says.

And when a landlord discovered what 3nder is, he backed out at the last minute, refusing to rent to Trifonov, the app developer says. He claims the landlord said: "I don't want this champ in my property" — discriminating against him because of his non-monogomous lifestyle. Cluttons, the estate agents that Trifonov found the property through, did not respond to a request for comment.

Trifonov argues TransferWise is also guilty of "double standards" — presenting itself as progressive while acting just like the banks it seeks to supplant.

TransferWise says that its rejection is down to "the requirements that our payment and banking partners place on us." In a statement, a company spokesperson said: "Our terms and conditions reflect the requirements that our payment and banking partners place on us, and on that basis we don't process payments that are connected to adult services. Our Terms of Use make it clear that we reserve the right to refuse users or individual payments at our discretion."

You won't find any nudity on 3nder. BI However, 3nder doesn't contain pornography. Users can select frank descriptors of their sexual preferences ("bondage," "threesomes," etc.), but when they add photos, they're actively warned: "No nudity, society is not ready yet. Don’t risk getting banned."

The business has a bank account, as well as an account with PayPal, which discriminates against the adult industry (although the latter is not a business account).

And significantly, it's free to download in Apple's App Store, which has a ban on "adult" content.

A TransferWise spokesperson would not explain why the company classified 3nder as an "adult" business, because the company "[doesn't] comment on individual cases." They also declined to say whether TransferWise would be happy to offer services to "adult" businesses if there were no restrictions placed on it by its partners.

TransferWise employees stripped down to their pants at Liverpool Street Station in June 2014. TransferWise

The adult industry is no stranger to battles with the financial industry. Its struggles with banks are well-documented, with everyone from sex workers to condom companies refused service by banks and payment processors.

"For nearly a decade, PayPal, JPMorgan Chase, Visa/MasterCard, and now Square, have systematically denied or closed accounts of small businesses, artists and independent contractors whose business happens to be about sex," journalist Violet Blue wrote for Engadget in a lengthy feature on the financial industry's discrimination against the adult industry. "These payment processing authorities have also coerced websites to cease featuring sexual content under threat of service withdrawal, all while blaming ambiguous rules or pressure from one another."

Dimo Trifonov, the founder of 3nder. 3nder Dimo Trifonov claims that 3nder is being unfairly treated due to the stigmas surrounding kink and non-monogamy in mainstream society.

TransferWise is "confusing" it with adult content when the only difference between it and other dating apps is that it caters to alternative sexualities, he argues.

"I have a legit [bank] account with Barclays, I have a legit account with Apple, and Apple is allowing me to sell on their [App] Store ... every dating app has the same purpose. Some are marketing it in a different way. We like to be more direct, you know, we like to be more honest with people — of course it's about sex. Everything is about sex when it comes to online dating."

The Bulgarian app developer views TransferWise as having "double standards."

"What's interesting is TransferWise position themselves as a forward-thinking company, like thinking that banks are really old-school, and that they're changing the whole game, right? And at the same time, they have even more tight rules than banks in this case."