Is this T-Mobile Caller Name Display really for free for the first 30 days ?

I got a text for T-Mobile and this is what they sent me on my cell phone: “Free T-Mobile msg: Who’s calling? Try Caller Name Display; like Caller ID for your mobile phone.Call 611 to sign up and get the first 30 days free.” I would really like to know because I’ve seen advertisements online claiming that you can do it for free but they only let you do a sample and then want you to pay for some full versions. I would like to know if any one ever use this too and if it’s really free for the first 30 days because I would like to only use this for one day and that’s it without paying.