Oh yes we all have had. All the networks will tell you they have no control over it, even if the network is owned by them.
Makes you wonder, in this day and age, using your mobile in the south of Ireland should be the same as the rest of the UK. Think of how I feel living in the North and each time im close to a cell or mask Im charged roaming costs. Portrush is one, miles away from the souuth, 50 plus mils if not double yet hit an Ireland network mask and Im roaming.