When your bank continues to report your available credit lower than it should be what is your remedy?

say I have a 5,000 credit line and use $1500. But institution constantly reports to bureaus the available credit is $1,000 or $2,000. In one case I am over-extended and the other at 75% credit utilization which lowers my score dramatically.

What's the best course of action when people at the bank are inept in correcting it?