Cannot change bank details - dividends paid into wrong account

We have been trying to notify Computershare that my mom's banking details have changed for weeks. There only seems to be an online form and no phone number and we've now completed it asking what the procedure is three times but we have had no joy. The dividends are currently being paid into an account to which my mom no longer has access which is a major problem. This needs to be rectified immediately. Resorting to this platform so that hopefully we can speak to an actual person.