If you use carrier billing for app purchases..

[Ed Boland]

If you're used to using carrier billing for app/game/music purchases on WP 8.1, beware of making any purchases with the new BETA store on any of the new Win10 mobile builds. Carrier billing will still work fine with the "old store", but the new BETA store isn't set up to use carrier billing. It will use whatever payment option you have set up with your MS account. (PayPal, Credit Card, etc)

 

[colossusr]

Even in the new build where the store is not beta anymore there is no option for carrier billing