Poor service

ER consulting accounts department or finance has been contacting me, for outstanding amount on my account which I paid last year. Even after the payments they kept sending me texts that I owe them which ended up being more than what I initially owed them.

I made another payment and sent a pop which they confirmed receipt.

This year again they started with their smses, is there no communication between finance team or no updates done on their system because the money should reflect, and they should stop harassing me.