Paid $550.00 credit did not use my credit. Sent a ...

Paid $550.00 credit did not use my credit. Sent a bill to me for full retail plus penalties. Paid $529.00 more and now they say i have a $400.00 credit. But i had to pay all the late fees and retail prices triple the regular price. Even though i had a $550.00 credit. Called 4 times over 9 months. Different person different answer nobody communicates. Ester #7811 a manager was absolutely zero help. Horrible at her job.