Is my neighbor's 4G LTE Cellspot degrading my service?

Thank you for the detailed answers. So from what was said, I think this is exactly the issue.

Someone close to me in my apartment building is using a 4G LTE Cellspot device to broadcast a T-mobile signal using their own home internet. And because I know that internet service is already spotty and unreliable with high ping and slow speeds in my building. My phone is connecting to this device because its only looking for the strongest signal. And is degrading my service and affecting my call quality.

My options to fix this are to enable "only 5G" which unfortunately Iphones do not support. (They allow the option to use 5G more when its the strongest signal available.)  Or contact T-mobile, which I know I'm most likely to just get a run around trying things from someone just trying to do their job and get to the next conversation the quickest and it won't work or change anything in the end. The only thing that I see working is T-mobile sends a request to the Cellspot device owner to stop using the device or send it back in. Which I doubt would happen.

Currently I will continue to leave my home to make calls to make sure they don't drop or have quality issues. And will look into switching services to a carrier that does not use the T-mobile service.

Something unfortunate about this is other T-mobile users in my building notice that they have a strong signal and just think the service is slow. When in reality T-mobile is not the direct cause for this service degradation.

I really wish T-mobile had the option to only allow users with the Cellspots devices account connect to it. Or only allow the use of a Cellspot device when they know another T-mobile customers address is a far distance apart. I cant see the Cellspot being supported for much longer. These devices only support 4G capabilities when 5G is now becoming the norm. And with wifi-calling on most smart phones this device just creates more problems than it solves.