straight talk says my sprint iphone 4 has to have a serial or MEID with only numbers and no letters for them t?

I won the phone on ebay for a seriously low bid after reading that taking an iphone to straight talk was very easy and now I am told what I asked in my question. Since I refuse to pay more than 50 bucks on cell service I could care less about, do I now basically just have a seriously cool mp3 player? LOL