Rain debited my account without permission and customer service is awful

Customer service is awful. I sent emails and messages on the WhatsApp to cancel my rain. I do a manual payment every month from 2 different accounts. If I don't have cash I don't pay for it until I do have cash. This morning they decided to *****ulently go into my account that I pay with sometimes and debit R625. Now I didn't think that they would do this because they don't debit and I don't have a debit order agreement if I remember correctly. It's a pay as you go sort of agreement. I didn't even need to submit payslips or anything so why do they feel they have the right to go into my Nedbank account. Also what is wrong with Nedbank for allowing anyone to go into my account without a debit order mandate. I want my money back now. Rains advertising is false as well they say unlimited calls but that's not the case. I want my money back that was my sons school fees money and rent money in my account. This is ludicrous.