Harrasing and phoneing on paid up client!!!!

My dads Direct Axis account was settled Decemeber 2023 and we have an paid up letter which was forwarded to the Vertex whatsupp number, but I guess they dont know how to either read or they just like harrasing people. They have phoned my dad 6 times within an hour and my mom 4 times. As my dad put the phone down somebody else phone my mom. PLEASE GET YOUR PEOPLE TO STOP HARRASING MY PARENTS!!!!!! GET YOUR FACTS SORTED OUT AND PHONE THE PEOPLE WHO NEEDS THE CALL!!!!!!! WHAT IS YOUR TELEPHINE BILL A MONTH OR ARE THEY GETTING PAID FOR EACH CALL THEY MAKE. SORT OUT THIS ACCOUNT AND STOP PHONING MY PARENTS...