Refund on out-of-stock items

I am having a terrible experience with the BOTTLES app....from Pick n Pay. 2 weeks ago i ordered some things, 1 item was out of stock. They never sent a msg saying it was out of stock, but charged me for it. They supposedly did a refund, which hasn't reflected to date. The purchase was on 13 February. They said refund takes 3-7 working days. Then when i messaged to say i received nothing yet, they said they would send proof of payment, and suddenly now the refund takes 3-10 working days. Absolutely not acceptable!!