Returning equipment after receiving unreturned equipment bill

I stopped services about a month ago but forgot to return my equipment. I received a bill for the unreturned equipment along with a 'partial' bill for $6.83. The partial bill was due to xfinity charging me services ahead of time, after I had submitted requests to cancel the service. Xfinity recently refunded $69 of the $77 that I was charged and the remaining was added to my current bill. 

I read in a previous forum that if I return the equipment now, the equipment bill will only be waived if there are no other charges on the bill. Does that mean that I can't be waived for the bill if I return the equipment? If I pay off the remaining partial charge, and what's remaining is just the equipment bill, would I be able to return the equipment and get it waived then?