So sorry to hear about your negative experience.
My friend knows someone who has been in possession of a long arm for several years and she has yet to fix her tension problems! Even more astonishing is that this long arm quilter doesn't believe her tension problems can be fixed!
I would rip it out (UGH, I know) and investigate other long arm quilters by meeting with them and asking to see samples of their work before handing it over to have the quilt properly finished. Hopefully you're not on a deadline...
Good luck to you.