Rate Lock protocol if i received lower rate

[Dominique C.]

Purchasing a property and mortgage broker A called to suggest rate lock on Friday- after discussing with him my options he said this was best rate he had -  and suggested I lock since market is all over the place with impeachment hearings. I felt comfortable with this so i gave a verbal ok to lock. He sent me Loan Agreement to sign - which i have not done yet.  

I had gotten some initial quotes in the beginning from Mortgage Broker B and he said he would send a loan estimate -  which i never saw - I discovered it today and his rate is ½ point lower and closing fees are about $3,000 less - what is the protocol to having Broker A meet new rate provided by Broker B? Broker A has already ordered my appraisal -