I have an HP Slate 7 HD tablet that I purchased in 2014 which came with 250MB of included data. Whenever I needed more data I could simply purchase a top-up via Foggmobile. However the top-up process has stopped working in the last couple of weeks. I spoke to HP IT technical support about it a few days ago and they advised me that the top-up process ceased to be available two years ago, but I have been using it regularly until about mid December 2017, so this appears to be complete nonsense. Has the top-up system been recently terminated and, if so, how do I purchase more data? If a top-up is no longer available via Foggmobile, can I install another data SIM in my machine to get up and running again? Will this work smoothly and seamlessly or will I need to unlock the machine? It was originally purchased from Argos rather than HP direct. Does this make a difference? Please don't advise that I use WiFi to get an internet connection as the only reason for buying the machine in the first place was that it could get a connection on-the-go via the mobile phone network.