Checked the sender exchange and no refund until now!
Did you try to
double spent your bitcoin? If that's the case you should have put a higher transaction fee 370satoshi per bytes just to make sure it will be
confirmed without issue.
I did try to double spent my bitcoin transaction before, however I can't sort of work that out because the computer I have don't have the necessary security patch also the Electrum did have a vulnerability this week it is quite a lot of trouble.