i have a question..my i860 keeps shutting off by itself and says "insert sim" like 10 times a day, and does it right in the middle of a call..i take the battery and sim out, and it still happens..so im gonna take it to get replaced..now, i don't have the service plan thing every month...do i have to pay anything when i swap the phone even tho i don't have the service plan?...and where do i go to swap it?..a regualr nextel store?