Mandate ****?

I filled in the mandate in order to receive my money from a client via Wise, which failed. I then tried to phone Bidvest Bank/the handler copious time, the phone does not get answered. I have emailed them as well, all I seem to get is a repetitive request to fill in the mandate, which then fails. I get no responses to emails and so far no one has phoned me back either. My client cannot cancel the payment as Wise states the amount has been received by Bidvest. Now what?