Cellular Data Plans Don't Have a Phone Number
A phone number is generally not "attached" to a data only carrier account and this is what the iPads with Cellular + WiFi utilize. Many people confuse having a (tele)phone number with a cellular plan, but a phone number is just a means for the customer to connect to another device on the telephone network.
As plans go, there are basically three types:
- Voice Only. This is just a basic plan that provides cellular service to make telephone calls with no data. Yep...they still exist!
- Voice & Data. This is your iPhone plan where you can make/receive calls as well as use the internet
- Data Only. This is your iPad, or hotspot type of plan (note, this is not tethering to your iPhone type of scenario)
Two of the three plans above will have a telephone number because of the need to make a voice call whereas the data only plan has no need for it. In other words, you can have an account without a telephone number, but you can't have a telephone number without an account.
Access to the Network
It's your SIM (or eSIM) card that gets you access to the network whether it's a voice/data or data only plan. The Subscriber Identity Module is what authenticates you to the carriers network and identifies not only the device, but the account that's being connected. If it's a data only account, there's no phone number.
I posted an answer to a very similar question relating to the Apple Watch's eSIM and calling another number on the PSTN (Public Switched Telephone Network).
Why some iPads have a Phone Number and Some Don't
So, when you look up your phone number by going to Settings → General → About → Cellular Data Number, you may get a phone number or it may come back "Unknown."
Why? This is because of the plan that is selected.
- If you put a SIM card in with a voice/data plan, a phone number will show
- If it's data only, "Unknown" will show.
Now, since your iPad isn't a phone; excluding FaceTime or similar apps, you can't make telephone calls with it as there's no "Phone App" like on the iPhone. However, you can take the SIM card out of your iPhone that has a voice/data plan attached to it and put it in your iPad and have it function. You'll be authorized to make voice calls and surf the web, but you just won't have the physical ability to make the calls. It's like getting phone and Internet service but only buying the PC and not the telephone.
Could your plan have a phone number but no voice plan?
Absolutely! Carriers make mistakes all the time in how they provision things. Even though things are mostly automated, there's still a human involved in setting things up and a phone number may get provisioned by accident. This doesn't mean your data plan has a (working) phone number because you won't be able to call it.
