Does the co-signer on a Les Schwab account have the authority to close it without the primaries authorization?

My former brother in law co-signed for me to open a Les Schwab account to get new tires for my car. Now that I am no longer with my partner he wants off the account, and is threatening to close it. I don't believe he has the authority to do so, as I am the primary account holder, but the store isn't open today to talk to a representative, and I can't find the information online. Do any of you have information/knowledge on this subject? I'd greatly appreciate it!