Not getting calls from ZTE Blade A5 2020

I recently bought a ZTE Blade A5 (2020) from Amazon. My carrier is MetroPCS, so I called customer service to switch my phone number to the new phone. Ever since I got it, it’s like I’m barely getting any calls. What I mean by that is people keep telling me they’ve been calling me, but my phone never rings or even show that anyone is calling. Whenever I call someone, it goes straight to voicemail but people tell me that I haven’t called them.

Does anyone know what’s going on or why my phone is doing that?