Data Service Doesn't Work

[Ginger26]

I bought my husband a motorola i580 phone from ebay. He put his sim card from his old nextel motorola phone into the new one, and can make and receive phone calls, but cannot get data service (internet, text messaging, etc.) After an hr of working with someone at a nextel store, they told him that the phone was still registered to someone else and that he would have to have the seller "release" it.

Of course the guy from ebay got his money and is not returning any of my husband's phone calls. Is there any way around this so he could get data service?

He shouldn't have to buy a new phone b/c of this. So any help would greatly be appreciated!