Being charged for a free line for 4 months, unhelpful customer support agents

I'm being charged for a line that was supposed to be free. I signed up for it along with my 1 Gig internet plan, and it was advertised as free for the first year. However, I've been incorrectly charged for the past 4 months, including activation, taxes, and fees, while my neighbor on the exact same plan is charged nothing.

Over the past 4 months, I've been charged a total of $199.93 (Jan: $76.78, Feb: $25.90, Mar: $54.32, Apr: $42.93). I've only received $64.00 in partial credits, leaving an outstanding overcharge of $135.93.

Every month, I spend close to an hour with customer support chat, get a partial credit applied, and then the same issue repeats the following month. I even visited a store in person, but was told they don't have visibility into mobile accounts and to contact support via chat.

Seeking A full refund of the remaining $135.93, and a permanent fix ensuring the line is free for the remainder of the promotional year.