The Tube in London could get even more expensive if you use Apple Pay

LONDON — If you're thinking of using Apple Pay to fund your transit fees on the Underground, be careful. It could end up costing you a small fortune.

People who have been using the paperless payment service since it launched in the UK on Tuesday have encountered several problems.

First, if your phone or watch runs out of battery after you've checked in, you could be charged the maximum fee.

As Transport for London (TfL) warns:

Your iPhone or Apple Watch must be switched on to use it to travel. You should also check that you have enough battery on your iPhone or Apple Watch to complete your journey. If you don't and it runs out of battery in the middle of a rail journey, you will not be able to touch out at the end and could be charged a maximum fare. Read more...