Billing error - being charged for returned xFi modem. Need direct messaging to continue with last messages.....

I need direct messaging again. I've had messages opened for a huge mess on my account. The last message was 22 days ago. It was a problem with billing, an extra xFi modem and my cell phone. Y'all were great and got everything straightened around - except the extra xFi modem that was returned is showing up on my bill. At least I'm assuming that's what it is. The charge is showing up under extra charges and came about when plans were switched around (part of the previous message.....) The plan I got was for a free xFi modem for 12 months. Help please..... my bill is $15 higher than it should be!! Thanks.