How can I save my own Ringtones on a Palm Centro (Verizon)?

I just got a new Palm Centro from Verizon and I was hoping that I can have my own Ring tones. I transferred an MP3 file through bluetooth from my PC to the Centro and it went into my Ptunes. I can listen to it but no option to save as ring tone. So then I sent a text message with my work cell to it, I received the message with the sound, no way to save it there either like I use to on my LG phone. Is there any FREE way to do this? I do not have a data plan so not wanting to pay per MB for downloads. I do have a text message plan. Thanks in advance.