I wonder... is this, in a way, a benefit of PAYG?
My current network (Vodafone) provides a decent signal at home and a borderline (but adequate) signal in the other place I regularly play with a phone, a certain pub in which I sit while other half does shopping.
But if Vodafone were to reorganise in such a way that any of my regular locations became notspots, whilst I would be grumpy, I could probably solve it by simply switching networks - pretty much overnight. With a contract however, switching might be more of a problem, I might have to wait until a fixed term expired?
I have never had a contract phone so above is based on assumptions, that may be wrong.