Do not pay that gent another red cent until you decide how much, if anything, you believe you owe. Then pay that amount with an explanation of why you do not owe more. If the lawyer sues you, be prepared to tell your story to a judge.

An alternative is to submit the dispute to fee arbitration by the local bar association, but the difficulty here is that most of the decisionmakers are lawyers. Their sympathies may lie with your lawyer's billfold.