Billing of faulty decoder

Good day

Dual view device S/N V ********** 46, Smartcard No. ********** 504 was found to be faulty and replaced by the following:

1. MCS IS20 V ********** 59X0; Smartcard No. ********** 910 2. MCS IS20 V ********** 73X0; Smartcard No. ********** 4739

I paid R297 via FNB app and the balance due was zero on 23 Feb. Mind you, before then we had a credit balance of R75. A day or two later, there's a new amount of R176 due. How? Remember countless emails complaining about Feb service which I've paid without watching as one of our decoders quoted above was faulty. Get your billing right and sort this.