Tradein device

Hello,

I recently joined the xfinity wifi, after the customer support mentioned there are having special deals for adding mobile lines and for tradein device. So I took two lines with xfinity mobile and planned to upgrade my device to s25 ultra. At that time customer support mentioned we can do the tradein anytime before march18th.

So from last two days I am talking with customer support to tradein my device, now the customer support is asking me to add another new line to get the 1000 dollars tradein offer.

I added two lines less than a month before now they are mentioning to add on more line to get the tradein offer.

I need to raise this compliant to higher officials, I need to know the procedure for raising the complaint.