I was a seller on ioffer and I found that someone used my debit card and made purchases on it from Bulgaria. It is amazing how a few days before this happened I was chatting with ioffer support and the same debit card gets used and all of a sudden my bank blocks the transactions suspecting fraudulent activity.
I would say never trust ioffer as they are a fraud company and their employees can steal your card information if they know you are not US based or are otherwise a sucker for cyber crime.
I did get my money back (approx $300) from my bank but I swear I will never use ioffer again.