Could not activate mobile data network

[SueJD1]

Just returned from an overseas holiday (Europe) where three of us had Travel SIM's installed on our three phones: Apple iPhone 5s, 6s and a 6s Plus.

On returning to Australia we each turned off our phones, removed the Travel SIM and replaced with our Telstra SIMs which worked perfectly before our trip.

All three phones have the same issue accessing the internet on 3G or 4G. We can make and receive calls okay.

The status in the top left shows 4G or 3G, but when you try to do anything that uses data like Google Maps or access a Safari page for example, a message appears: Could not activate mobile data network'.

When have each tried everything - re-start, re-insert Sim, check Mobile Data is ON, reset nework settings, reset APN to Telstra.wap to no avail - accessing the internet via data doesn't work, on all three phones.

We suspect aliens are involved or that Telstra has blocked our data connections. 

Any ideas please?

[SueJD1]

Resolved over the phone with Telstra Support.

To fix, Go into Settings>General and look for the Travel Sim Profile and delete this Profile. Then go to Settings>Mobile Data Options>Mobile Data Network>Reset Settings>Reset

This restored or data access to the internet.