Buyer asks to be sent product pictures through their phone number

[jvalles6]

 I was selling a phone and sold it to the best offer. However, the buyer asked me to send pictures to their phone before they can make the payment and listed their phone number. I'm unsure as to why they can't see the product, but I told them that I can't contact them outside of Ebay and would be glad to give them more details. They insisted that I contact them through the phone number before making the payment. Do I cancel the order or is there something else I should do?