How to use ringtones on pantech p7000?

[Sahar]

On my old phone (LG CU515) I was able to create ringtones on makeownringtone.com, i would put them on my micro sd card, and then save them onto my phone. After that I was able to use them as a ringtone. I recently got a pantech p7000. I've done all the same steps but it won't let me use it as a ringtone. The "set as ringtone" option is completely gray, I can't select it. Size isn't a problem because one of the ringtones is 35 kb which is nothing, it won't work either. They are in mp3 format. Thank you in advance