Last week, I wanted to sell 2 mobile phones that I have to CEX. However when I went to the local store, there was a sign put up saying "Sorry, we are currently unable to give cash, only store credit". This is because (according to the salesperson) no one has been buying stuff. So I went back home and ordered the envelopes from their website. The envelopes came today but I also checked the store again and they are giving cash again.
My question: Can I still sell directly to the store even though I've ordered the envelopes?
If I do send them through the mail, will they deduct the postage cost from the money they will send me?