When will my first and second month’s bill be due, if I decided to switch to t-mobile?

This is what happened to me. I placed a sim card order October 30, 2021, it arrived & activated service  November 2, 2021. About 10 days in, I received a notice my bill was coming up due & I needed to pay $70 to avoid service suspension. Didn't have it then, service was cut off November 25th/26th & paid $89 [service + bs restoral fee]. About 4/5 days ago, T-Mobile started blowing up my phone [4x-6x a day] which I thought was weird because I was paid up. I logged in last night to check upgrade prices & was surprised by a notice that said I have an outstanding unpaid balance of $29.85 I needed to pay immediately to avoid service suspension. I looked at my total balance & almost passed out. Remember, I've had active telephone service with T-Mobile since November 2. Yes I ordered the sim card October 30 however did not receive it nor activate service until November 2. I understand maybe starting the bill cycle a little bit earlier however if you don't have activated service oh, I don't see how they can legally charge you. I didn't have a phone number nor an activated, officially established account with T-Mobile yet. So, I started trying to get to the bottom of why my bill shows $181.10 after only  including the $89 payment made 1 December 2021, 33 days since ordering the SIM card & 30 days since I activated service. I do have some third-party charges totaling about $31 + $9 towards Netflix however that's it. That doesn't equal the difference between my monthly total and what they claim I owe. Monthly service would be $65 with auto pay  but I wasn't sure I'd have the money by the same day each month so I turned autopay off. As a result, my monthly service is now $70 a month which is fine as I knew that would happen if I do pay was turned off. That said,  when I downloaded the detailed December bill, it showed a balance forward of- $92.49. When I started looking at the detailed billing information, I was astounded!!! I went to the bill summary page &  down towards the bottom, it says, "Here's how your monthly plan cost is changing" &  shows three black vertical bar graphs. September 30 - October 30, October 31 - November 30 & November 30 - December 30.  that's another thing I just noticed. Why does Sept - Oct end on Oct 30 so Oct. - Nov. - starts Oct. 31st but Nov. - Dec. starts 30 Nov. instead of 1 December. To begin with,  T-Mobile cannot legally charge me for a month of service from 30 September to 30 October  considering 30 September -29 October,  I hadn't even attempted to place the SIM card order nor thought about it yet as I was still with AT&T.  I understand maybe starting a couple days early like the day an order is placed but businesses cannot legally charge someone for any amount of service during any time period PRIOR to them having ANY interaction WHATSOEVER with the company & I am not guessing , I'm a law student, previously did & still do investigative legal research.   Civil/Consumer [most Tort Law], Business & Family Law are my  specialization areas. Even if I wasn't, this is basic common sense. If you adopt a child, you don't then discipline them for something they did before you adopted them the minute you bring them home. I already knew historically, T-Mobile has been billing braindead with batshit crazy billing practices but this tops anything I've ever read & heard about. My last confused curiosity is…my most recent from 8/9 days ago includes charges for December. How is it postpaid billing when charges for that month generate prior to the month ending?

MJM

Texas