Clarifying account/internet status after moving

Hello! I'm an Xfinity internet customer, and I've just moved from one apartment unit to another in the same building. The building is "set up" for Verizon, but two years ago when I moved into my previous unit, an Xfinity technician was able to come and set me up with a gateway and I never encountered WiFi issues. When I set up this move in the Xfinity app one month ago, I was informed that I could simply bring my modem with me to transfer my internet services.

When I attempted to set up my modem yesterday w/ a coaxial cable and activate services, I was shocked to find in the Xfinity app that my account was no longer considered active. I started a chat with a live agent and after a long, complicated exchange was informed that:

1. My account was considered inactive because it was attached to my old address (was not given instructions on how to access the account linked to my new address, but figured that out myself, more below)

2. I would need to set up another technical appointment to activate my services

This did not turn out to be true, because after ending the conversation and exploring the Xfinity app further, I found an option to "link accounts," which enabled me to access the account for my new address. After accessing this, I was able to establish an internet connection using my gateway very easily and without assistance.

The hard part is over, but I'm still left with some clarifying questions about my account status and what exactly is going on:

Why do I need two separate accounts just because I changed addresses? I have a bill due next month through my old account, will it be charged there or through my new account? Would it be wise to keep the technician appointment that was set up for me, just to get someone into my apartment to ensure I can maintain steady and reliable service? After all, I was informed by a live agent that I would need in-person support. Despite this not being true in the interim, I want to avoid further issues.

Any guidance on this situation from people who have had similar experiences during a move would be greatly appreciated. Is this all less complicated than I think, and I just had a poor customer support experience? Sorry for the longwindedness!