Did I get scammed? Email about over data limit at beginning of cycle

So I recieved an email about going over my data or reaching my limit. Which i thought was odd because my billing cycle should have restarted a couple of days ago. It looked completely legitimate, from xfinity mobile. I had a hell of a time getting to talk to a representative and when i finally did, she said since the email was a .com and not .net it was a scam. But the URL i clicked before being told that took me directly to my xfinity account. And upon reviewing other emails, ive had other emails from xfinitymobile with a .com on them about my bill being due.

What email should i trust from xfinitymobile?

What should i do if the email was a scam?

Also is there a way to check my speed?

Also why is it so hard to get ahold of customer service?