Can a petitioner file a counter lawsuit to an atty. who terminated his representation on a pending Greencard due to address change made thru USCIS?

If my atty.(from a law firm) did not process the change of address on my pending I-485, Application to Register Permanent Residence or Adjust Status through USCIS for the reason that they want to receive the remaining balance (we owe them) first before they do it, what right do I have as an applicant against them? When accdg. to the contract, the remaining pymnt is due upon the approval of the case. My case is not approved yet, it is still pending.When I initiated the change of address over the phone through the USCIS myself, they immediately terminated their representation for violation of payment policy and communicating to USCIS about the update, when in fact weeks prior to moving to a new address and on the 3rd day in the new address they have been notified already about it. Can I file a lawsuit against them for doing this to me? If I don't pay the balance, will that be grounds for them to sue me? CAn I counter charge them? Please send me any suggestion. Thank you