Craigslist account could not be verified

I have registered a Tropo. account and get a phone number （256）580-7379, but can not verify the Craigslist account, it says: :AR15firin
?Your phone number could not be verified.
Please start over with another number.?
Tropo. can not work for Craigslist？：:headache:
Anyone tell me how to do?

Thank you all of you！