Usually when I travel to the UK I buy 3's "Internet with Legs" SIM card from Amazon which is preloaded with 24GB of data and just works as soon as I put it into my Huawei 4G mobile hotspot. I also bought a second SIM card at WHSmith at Heathrow T5 from EE which seems to be marketed by SIMLocal. Same thing, put it in and it just works.

Given how easy this was, I decided to buy SIM cards for our phones instead of just the mobile hotspot. I bought a 3 UK 50GB SIM card at Morrison's for 99 pence, and bought a 15 pound voucher. This was cheaper than the other SIMs I paid for. The packaging made it look like I get 50GB of data if I buy the 15 GBP voucher. I applied the voucher, received a message that I would be charged 5p per MB, and then following day I was asked to top up again since I had gone through 15 GBP or exorbitantly priced data.

This is the response 3 sent me after I complained on Twitter:

"This is an automated message, the top up credit value applies first then converts to the add-on if purchasing the pre-paid data pack. This relates to having just credit on the account without conversion to the add-on (Data Pack) for 30 days."

So, how I do convert it to a Data Pack? There is no information about this on the packaging and even in the portal. It feels like an elaborate scam. I'd like to be able to trust the system when I can't pre-purchase a SIM card from Amazon or Heathrow.