waiting for the manager to contact me about a billing problem I have, I call a couple of days ago and the young lady said that the manager will call me

You'll have to wait till they reopen. Do not try to jimmy open the back window and shimmy down the drain pipe. Wait till they reopen then pander to the manager regarding your billing request blunder.

With all gyms closed, I would go straight to corporate until store opens in the next weeks.