Unable to refund deposit

I cancelled my landline, ADSL and cellphone contract back in April of 2018. After the confirmation of my subscriptions I still received invoiced for my cellphone number. It was under R1 so I didn't know what to make of it. I phoned Telkom and they said to ignore it. After 3 months or so I realized that I never got my R700 deposit back from the landline subscription. I phoned Telkom again and was promised my 'then cellphone invoice' (which shouldn't exist) was around R5 outstanding and thus they could not pay back the R700 deposit. The operator said he will clear the cellphone contract invoice and the deposit will be paid back into my account. I haven't received any cellphone invoices again. I also haven't received any deposit too. This was November last year. Telkom please pay your client back on time. This is ridiculous. I can't understand how you can keep your clients deposits by default.