I've made a payment to my account on the 31st May 2021

I've made a payment to my account on the 31st May 2021. I got two calls last week Stating that I have not paid ky account. I've sent the Proof of payment I think 5 times this week to multiple emails received when i call in to the financial services office number. Can ANYONE ASSIST BECAUSE I AM FED UP WITH CALLING AND NO ONE CAN ASSIST