MTN POOR SERVICE AND THEFT

I DONT HAVE A SATISFACTORY CUSTOMER SERVICE ANYMORE. I ONCE PURCHASE AN IPHONE AT ONE OF THEIR BRANCHES ON A 2 YEARS CONTRACT FROM 2***. SOME MONTHS THEY DEDUCTED DOUBLE THE AMOUNT OF THE POLICY AND WHEN I BROUGHT THE ISSUE TO ONE OF THEIR BRANCH . THEY SAID THEY WILL INVESTIGATE AND THAT WAS LAST YEAR ALREADY AND I ASKED THEM TO CANCEL THE CONTRACT WHEN IT ELAPSED THEY ASSURED TO ME THAT THEY DID BUT TO MY SURPRISE THEY KEPT ON DEDUCTINT MONEY FROM MY ACCOUNT. I HAVE BEEN ALMOST 7 TIMES TO THEIR SHOPS TRYING TO CANCEL THE CONTRACT THEY ONLY MANAGED 2 MONTHS AGO AND I HAD TO PAY FOR WHAT THEY SAID I OWE THEM INORDER TO CANCEL THE CONTRACT. CURRENTLY ABOUT THREE MONTHS AGO I BOUGHT A PHONE AND I SPECIFICALLY TOLD THE SALE'S PERSON I WANTED A PHONE THAT IS NOT NETWORK BLOCKED . WHEN I USED THE PHONE FOR 2 WEEKS I DISCOVERED THAT THE PHONE DOESNT WORK WITH OTHER SIM CARD EXCEPT MTN. I WENT BACK TO REPORT MY DISAPPOINTMENT AND ASKED THEM FOR A REFUND OR A NEW PHONE BUT THEY REFUSED AND SAID THEY NEEDED TO TAKE IN THE PHONE FOR ASSESSMENT . I GAVE THEM THE PHONE LAST MONTH ALREADY BUT THEY NEVER CALL ME BACK TO ADVISE . I WENT THERE LAST FRIDAY 15TH AND THEY PROMISED TO CALL ME BACK ON THE 16TH/10/2021 BUT THEY DIDNT AND I TRIED CALLING THEM THEY DONT PICK UP. IT'S LIKE I BOUGHT THE PHONE FOR THEM TO KEEP IT.