Device says "2G" next to it

I have a 3G modem installed. I switched over to a 1 GB data plan and now my device says “2G” next to it. The SIM card doesn’t seem to be working with the modem. What’s going on?

And what happened to Hologram support?

3G modem installed in what? Says “2G” next to what?

Your message is so unspecific that it’s impossible to help.

What hardware, operating system, SIM card, provider, and software are you using? What are you even trying to do?

Really, imagine you are a stranger to your problem and all you know is what you read in the question. What would you do?