How long does it take for a refund on a wrongfully charged subscription on App Store?

I double clicked a monthly subscription it took the payment twice. 2 days later a statement said 1 payment would be refunded. Checked subscription notification has disappeared but is only now showing 1 payment but that’s 10 days now and still no refund. Was bought in store purchase so automatically comes off. No contract just cancel or continue each month but wondering how long I should wait on refund and obviously the statement has vanished all I have now is proof on my bank statement. If you want to question it who do you call or is it just a waiting game ? Thanks