BAD CUSTOMER SERVICE

i have been with supersonic for years & alwasy paid R695 ontime, 25th each mnth, last they received was 25/03/2024,in the week they informed me that my package is old 20/10 and now upgraded me to 50/50 same price.They then sent me invoice i owe R695 BY 7APRIL 2024, I WAS TAKEN ABACK AS I HAVE PAID END MARCH, THEY said I NOW HAVE TO PAY IN ADVANCE AND NO LONGER IN ARREARS, AND THEY WILL SUSPEND MY LINE 07/04/2024, SO I SAID NOW AFTER 4 MONTHS UR SYSTEM CHANGED? THEN THEY SAID I OWE R1219, NO WHERE DID I EVER SKIP!!!! AND IT WAS NOT BROUGHTTO MY ATTENTION AND NOT EVEN ON MY INVOICE OR STATEMENT? I HAVE ALL MY STATEMENTS. I WANT THIS RESOLVED BFRE 7 APRIL 2024