Unfair treatment

Not a very good start as a new client I signed up in January 2025 as new client to start cover from 01/04/2025, for a low premium cover for 2x months both April and May they could not debit by account multiple times they even tried different dates but nothing, I even asked them after these falling attempts to provide me with their banking details witch I was told they do not accept EFT payments. Then on 27/05/2025 I emailed them to rather cancel the cover as I can't sit without car Insurance, which they failed to cancel, then all out of the blue today 4/6/2025 a large amount went off my account, I phoned them and asked what is this now as I have cancelled because you could not debit my account which I was told that the low premium cover was cancelled and that the promotion is no longer valid now I have to pay for a much higher premium this is not fair for 2x months they could not debit my account for the low premium but they can debit my account for the higher premium how does this work? I will stay a client, but this is not how you treat a new client.