Paying a debt which is not mine

My elderly grandmother, who is in a frail care ward at an old age home, has been hounded for years by Woolworths debt collectors. I finally managed to get them to contact me instead of her as she is confused and deaf and can't hold a conversation in person, let alone over a telephone. I am her attorney as well, My grandmother unfortunately has absolutely nothing and her accommodation and medical fees are being paid by my mom and her siblings. In a nutshell, Woolworths debt collectors (Not Blake & Associates) have managed to put a debit order of R1000.00 on MY bank account for my grandmother's debt, for which I am in no way liable for. I have been emailing back and forth, making numerous telephone calls but all to no avail. A total of R4000.00 has been deducted from my bank account. To date Woolworths has done NOTHING to stop this debit order or to refund me with the R4000.00 which was ********ly deducted. I don't have the time to go visit my bank and to stand in line for hours to try to stop a debit order. This is ridiculous and I am livid, to say the least, I will be taking legal action.