I know nothing about tablets.
My last visit to ATT came out to a 50 dollar flip phone and 30 a month two year to service same. I already have had their internet service for decades. The phone issue is not competitive in monthly pricing because I am part of the Reagan era lifeline program which serves the smart phone for free. I don't do voice only texts. The saved money is used towards the medical billing.
In the past we have had cell phones in trucking and it was good. As long you stayed out of range of a Canadian tower which would generate a 1000 dollar bill which lands into our post box. (Roaming and international and so on.)
I keep the phone for when I need it otherwise it's the net. But it's not for trucking. I have done internet on the road via dailup in the late 90's and truckstops do not like to see their table phones rewired to route the line to the laptop.