Just tell them that the problem is still with you and see what they say - if they balk or seem to be reluctant to help you out without charging more $ then start up about the no payment thing. If it a reputable shop they should try to help you resolve your problem without resorting to this avenue of resolution. The next thing would be to find another tech/shop.
Jim
'85 300D
'95 E320
'97 CRV