I've been getting those texts as well, ironically, i'm with T-mobile like two of the other posting parties here. I just went to their website,
www.pday28.com, and there's a link on the top right hand corner in blue print called report spam, it'll pop up another small window, from there in the 2nd paragraph, "If you have received email directly from easysmsloan.com and do not wish to receive further communication from easysmsloan.com you may remove yourself from all our lists from this page." is another link to remove your number, be careful, they are a bit tricky, sometimes they highlight the link and sometimes they don't, but in any case you can get to the link by selecting the last 2 words of that paragraph, "this page", from there you enter your number without dashes and you're home free.