Direct deposit for deceased?

I have a client who is the executor/administrator of his late mother’s estate. No assets, and she didn’t even qualify for the CPP death benefit. However, there is a refund on the terminal T1.

My client wants to change the direct deposit info on file with CRA, but TaxCycle says T1DD can’t be filed for a deceased taxpayer. Is this just for the T1DD filed electronically with the T1? Can the direct deposit information be updated by mailing or faxing the form to CRA? Or does CRA shut down all direct deposits for deceased taxpayers? I’ve seen that CRA continues to direct deposit the GST credit if they haven’t been informed of a taxpayer’s death, but I don’t know if income tax refunds are automatically switched to paper cheque.

I have been trying to call CRA about this all week, but the wait time is always over an hour, and their call-back service doesn’t seem to be working. Does anyone have some insight?

Cheques only after they become aware.