Hey there, Nevernoonenothingever,
It sounds like you're having a few issues with your iPhone SE. Let's address them each individually:
The following Apple Support articles are designed to assist with an inability to make phone calls or send text messages:
You may need to get in touch with your wireless carrier if those resources do not assist.
There are certain circumstances under which it is expected that your iPhone will get warmer. Please review the information in the below Apple Support article to learn more about when that is, how to identify when it's not normal, and what to do:
Your battery is considered a consumable part. That means that it is expected for its performance to degrade over time and with usage. How fast this occurs depends upon how you use and charge your iPhone, and you can monitor your battery health under Settings > Battery > Battery Health. If you have concerns over the battery performance, the following Apple Support articles may help:
For more help after that, please get in touch with Apple Support directly here: Get Support.
Have a wonderful weekend!