You can still use your agent. When his licensed is attached to the new agency you should sign a new buyer agency contract and disclosure form with the new agency. It is also important to discuss the changes with the broker of the original firm that you signed the original paperwork. The agent works under the broker of record on his license and that is now changing.
I agree with Ron. Inform the Broker of the company that your agent is departing from and tell him that you wish to continue to work with your agent even though he is switching companies and request to cancel your buyer's agency agreement with that real estate firm. And do let your agent know that you will be contacting his former Broker about it.
The Broker probably will comply with your request.
Prudential Connecticut Realty
Tell the Broker that you want to still work with the Agent.
This should nip any problems in the bud.
Most Brokers are understand and do not want complication.
Good luck and may God bless