How to properly change lawyers/

My BF is divorced and we realize now that he got not necessarily bad advice, just very little advice, and is left with a very unclear custody consent order. As his Ex likes to have her lawyer send letters about any and every perceived discrepancy, and the agreement is vague this has become expensive. So, he wants to get a new lawyer who will offer more concrete advice ( and frankly is less expensive). He has had one person recommended and is going to meet her tomorrow.
How does he properly termintate the first one? He sent an email about 2 weeks ago ( after getting a whopper of a bill for reading a letter) that said" I have received your invoice and will remit payment. From this point forward please forward all correspondance from Ex’s lawyer to me until I have hired new counsel."
He hasn’t heard anything back. Is that sufficient? What else needs to be done?

The new attorney will need to file a substitution of counsel in the court file and serve his ex’s attorney with a copy.