Network outages can cause unexpected problems;
Town i live had a fire at the telco exchange, which was also doing backhaul for 2 of the 3 mobile providers. It took almost a month to rebuild it.
ATM's, EFT stopped working so people could pay for things, like petrol, food etc... The town became a 'dead zone' for a few hours, you stop here you cant get going again.
Once everyone worked out one of the mobile providers was still working they sold out of 'starter packs' pretty much instantly and more had to delivered by courier.
But retails where prioritised and most where able to switch and accept payments within a day AFAIK.
Police flew some sort of emergency communications system down by helicopter.
A mobile ATM was also bought down (normally used for disaster zones) to take pressure of ATM's, might have been satellite based i dont know.
Banks where allowing people to withdraw money without checking their balance, some people abused it and got in big trouble later.