NO PAID UP LETTER

I FULLY PAID WHAY I OWE TO MTN LASY YEAR DECEMBER 2021.......8 MONTHS LATER OF ME CALLING THEIR DEBT COLLECTORS OFFICES TELLING ME THEY SENDING EMAILS TO MTN STILL HAVE NOTHING FROM THEM. WHEN I CALL THEIR FINANCE DEPARTMENT I CANNOT GET THROUGH. I JUST NEED MY PAID UP LETTER. ASOMBLIEF