Hello Lindam,
Depending on your son's location relative to the cellular towers, he could be roaming on extended coverage (Fido-EXT). As far as I am aware, these are the locations of the cellular towers around the college:
He should note that use on extended coverage is only meant on a temporary basis. The majority of usage needs to be on the Fido/Rogers networks.
If he lives or has classes in an area where his phone exclusively connects to extended coverage, there isn't much that can be done to connect to the Fido/Rogers network. If the area does receive some signal, a signal booster might be of benefit. It is a common misconception that any mobile provider will suit everyone everywhere. The mobile providers have their cellular towers strategically placed. Unfortunately, those locations might not be ideal for all customers. That's why there are the roaming agreements in place -- to provide better coverage for customers.
I understand some people in those situations disagree with the limited usage on extended coverage. However, I don't think it's Fido or Rogers who place the limit on usage. It's likely within the roaming agreements. No provider is going to want indefinite roaming on their networks. If you spend most of your usage on another network, they would rather you pay them for your services.
Hope this helps 
Cheers
Hello again,
Many factors -- ie distance from towers, potential signal interference, the band or frequency to which the phone is connected, etc -- can signal reception at any given location.
If it's happening at random places, he might take a mental note of where his phone roams on the extended network. If he still spends most of his usage at locations accessible to the Fido/Rogers networks, he shouldn't have any issues.
Hope this helps
Cheers
