can you make regular phone calls on an iPad mini with cellular

Only if it is paired with an iPhone. An iPad WiFi+cellular model can only access cellular data networks. To access cellular voice networks, it must be paired with an iPhone. By itself, an iPad can only make VoIP (internet) calls using apps like FaceTime, Skype, Ooma.

Make and receive phone calls on iPad - Apple Support

iPads are tablet computers ONLY. Not cell phones.

That is what an iPhone/smartphone is for.

Almost everyone, in the world, owns an iPhone or smartphone these days.

Apple allows cellular data plan use for using the iPad and accessing the Internet, on the go.

Also, you CAN still make FaceTime and/or Skype calls/video calls over cellular data, as well.

You can certainly let Apple know how you feel.

Send unacknowledged feedback to Apple here.

Tap the link below.

Feedback - iPad - Apple

I really think that it has no sense to insert a SIM card in an iPad, just to get internet data. Maybe for apple it is impossible or very difficult to make the iPad able to make normal phone calls; even though nowadays there are SIM cards that use VoLTE, to make phone calls; Which could be a solution if normal phone calls are to difficult to program in an iPad.

I really hope Apple looks for a solution, and in order for Apple to make it easy, the solution could be: to use the VoLTE option, already said.

best regards

Luis