[randomhunt]

In Belgium BASE, which is owned by KPN, do a reasonable deal compared to the others with BASE 0. Its technically a monthly invoiced plan but works as a pay as you go card - you only get charged for what you use. Its basically the same price as any of the "outside the bundle" costs for their other plans. If you either use phone calls/internet/text infrequently or highly variable it's very interesting.

https://www.base.be/en/mobile/monthly-plans/base-0.html

Interestingly also in Belgium there is legal requirement that the phone company evaluates your bill every X months and notifies you if you could save money by moving to a different plan. Invariably I used to always be recommended BASE 0 due to my highly variable usage.

I think the UK had a similar thing from O2 but I don't remember if it was a legal requirement. It could be a European thing.