If you are thinking of giving this a try (as I was) I would suggest that you don't bother unless you want to open yourself up to a world of grief.
I ordered the 'booster' via the website on Friday evening. Luckily I took a PDF print of the order confirmation page because I received no email confirmation, and there was nothing showing on my account order tracker.
Nothing happened at all Saturday so Sunday evening I thought I would check the order tracker. There was now an order there with the same Sales reference, but was showing as only having been placed a few hours earlier.
Going into the detail of the order however revealed that it was not for a 4G boost, but a 're-order' of my Broadband & Calls package - basically BT had instituted a new 18 month contract for my broadband and calls (and hadn't given me a 4G booster at all!).
Of course I contacted customer services immediately and very quickly got booted from India to the UK Mobile team. They thought it was irregular (I still haven't received any order emails) and said they had no order for the 4G booster. They contacted the Broadband Sales team who, after much confusion, came back and told me there had been a 'technical glitch'! But it was OK as I wouldn't get charged more. (Oh that's OK, you just extend my contract without permission then... No attempt to correct it).
To top it off the attempt by BT Mobile to re-order the 4G Booster still hasn't come through successfully.
Clearly BTs systems are not up to handling the Mobile Booster, and the cynic in me thinks someone in Sales could be making more commission by posting erroneous package sales.
Until BT has a simple, reliable way of adding Boosters to BT Mobile accounts I would recommend you don't try - I have only tried twice (once a year ago with the old European roaming pack) and both attempts have only given me major grief.
