Verizon is now offering a free version of its Call Filter spam blocking service, which was previously a paid service that cost $3 per month.

The paid version has a few extra features over the free version, but they share the same spam-blocking purpose.

The free version of Call Filter is only available for post-paid Verizon customers, and not pre-paid customers.

Verizon announced on Thursday that it now offers a free version of Call Filter, its robocall- and spam-call blocking service, which used to cost customers $3 per month.

With the free version of Call Filter, Verizon customers get spam detection, blocking, and reporting.

The paid "premium" version of Call Filter still exists, and contains a few extra features over the new free version, like spam caller ID, personal spam lists, personal block lists, a risk meter for incoming calls, and a lookup tool to get more details on a call that was potentially spam.

Along with the free version of Call Filter, Verizon is also rolling out the universal Stir/Shaken caller identification technology, that's also being adopted by other carriers. Stir/Shaken is designed to verify that the number you see when you get a call actually comes from the same phone number making the call. It should help thwart spam callers who use internet-based phone systems (like Google Voice, but they might use a different service) that let spammers choose what number will appear on a victim's phone.

For Stir/Shaken to work well, it needs to be adopted by other carriers, too, so that a spam phone number can be verified if a spam call is made on a different carrier or network. So far, T-Mobile has already added the technology to its network. AT&T and Comcast said they're adding Stir/Shaken to their networks for calls made between their networks.

Unfortunately for Verizon customers with pre-paid plans, the free version of Call Filter won't be available to them. Only post-paid customers will get access to free spam blocking.

To activate the free version of Call Filter, Verizon leads its customers to the main Call Filter page.

The problem of spam calls has only been getting worse recently, so it's good to see that Verizon is finally taking steps to reduce the number of spam calls its customers receive.