Billing issue after porting

Hola folks,

• I ported my two phone lines out of T-Mobile around April 23
• (This was due to one of them having a busted Caller ID where everyone I call, including family, would see the number as having a blocked Caller ID, this was never fixed after repeated calls and attempts over months)
• After porting, I received what I assumed was a final bill of negativo $91.18 around May 11 (T-Mobile says they don’t pro-rate cancellations, but for some reason they did here) because of course T-Mobile bills for the following month, so I already paid for service ahead of time between April 12 and May 11
• Then I get a direct debit attempt on my bank account for $178.19, for what, I don’t know, because I just got a bill for negative $91.18, meaning T-Mobile would owe me a check; seems like a mistake to me, so I reject the debit attempt, presumably this was for the billing cycle beginning May 12, and I didn’t have any active service I should be paying for
• Today, June 21, I get a collections notice and a bill in the mail for $119.01, which is $178.19, minus $91.18, plus a $25 returned payment fee, and a $7 late fee
• I call T-Mobile to explain all this, I’m told that the $178.19 was because I didn’t cancel my watch lines (!!)
• I explained that watch lines do not work without a parent phone line, and my watches lost their data plans on April 23 when I ported my numbers out
• I asked the customer support agent if she saw any usage on the watches at all, she said there was none, not even one kilobyte of data, no calls, nothing
• I asked what the watch lines cost, I was told they were $10 a month
• So, I asked how exactly I was being charged $178.19 from May 12 forward when I didn’t have any voice lines, and no usage or functionality on watch lines, and the only answer I received was that I failed to cancel the watch lines when I ported out my voice lines, despite the fact that they appeared as canceled on my watches
• On my current bill my plans show up as $0, equipment $0, services $0, but that the price of my connected devices increased by $2 a month

So, why is T-Mobile insisting that I owe them $119.01? The customer service agent asked me, "what are you willing to pay?" And I said zero because I haven't yet heard of anything that makes sense from her, and I didn't use any service with T-Mobile after April 23. Even if they wanted to charge me for two watches, that's somewhere between $10 and $25 per line, so, $20 to $50? They refused to wipe out the bill, but "cancelled" my service finally so I wouldn't be billed more.