Telkom ***** from employees

I took a contract with Telkom on the 31st of January 2025 and paid my first installment on the 1st of February 2025, I went to the store to return the contract phone because it was broken that was during the month of February and I also ask them why and where do they take my fnb account number of which I never provided them with my fnb account number, I gave them my tymebank for them to debit on the tymebank account. They told me the will fix it and they don't know how my fnb account appeared on their system. I provided my tymebank account number because I got paid from that account and agreed they will deduct every 1st of every month but they are trying to deducted from my fnb account number on 1st, 15, 31st every month of which that's not the agreement. I tried calling, going to the store but no one is helping me but tell me I owe R1546 while they took the phone back and closed the SIM card when I returned the phone. Please help as I've been getting calls, sms and threats that I owe them.