Computicket poor service

I have tried unsuccessfully to get thru to call centre number since this morning. I booked 7 tickets with my discover y credit card for Ed Sheeran concert... The payment was unsuccessful so received the email with link in order to effect payment correctly. It gave error code and instructed me to call them on call centre. But surely being on hold for 8 minutes is really not good enough.

Can someone please call me I even emailed and Robyn Bezuidenout rep**** but despite giving her my cellphone number I have yet to receive a call. I only have 6 hrs in pe to effect payment failing which I lose my booking ?