Sea service letter

Curious to see if anyone has had a similar issue

I recently submitted my application to upgrade to master and my previous employer mailed me a sea service letter that stated my position was “training mate”. They had issued a sea service letter to me when I was still employed with them and stated my position as “mate”

The coast guard does not accept training mate time to upgrade to master and I believe my previous employer did that on purpose because of me leaving.

I have emailed and left voicemails a dozen times with no response. Is there anything I can do besides renting a car on my next crew change and going into the office?