I think things have changed as there are SIMS for phones and SIMS for Tablets and dongles so I am led to believe certainly on 3 I have been informed.
There are pay monthly price plans for these, but the actual SIM is the same. On PAYG there should be no difference.
shows the Vodafone masts in the Sunderland area.
The majority are transmitting Band 20 only, there are a couple that have Band 1 for additional capacity.
Here is the map
of the O2 masts, and they have Bands 1, 20, 3 and 40. Your dongle won't connect on Band 40.
As you can see the Vodafone and O2 masts are in the same locations, they are sharing the towers and panels (at the top) but have different boxes of electronics on the ground.
of Three masts is here, as I suspected majority are Band 3
Congestion on a Sat night, in a Covid lockdown situation is quite likely sadly. Also your dongle is lowest category LTE.
Unfortunately I suspect the only way to find out more is to find someone with a 4G phone on the networks of interest whom can either loan you the phone to check signal in your home, or at least outside your home
21 years of broadband connectivity since 1999 trial - Live BQM