I don't think he can do much with the database. If at all he wanted to do something he can do that while he is working for you also. When you have a doubt on his honesty, you better remove the service now itself. Otherwise, if you continue with him you will be feeding further database, he will have more access to your works. So continuing with him is giving him will be a double advantage to him. He will access to already given data and he will have some more data with him further. The service provider can't-do anything. But before removing you should see the terms in the contract and you have to see on which ground you are terminating him. Otherwise, it will become a breach of the agreement.