@sam6, just to elaborate a little on the signal loss issue, mobile phones and mobile networks work on a variety of different frequencies with the range of microwave frequencies allotted to mobile phones. Higher frequencies don’t penetrate dense structures as well as lower frequencies do. If the cell network you’re connected to is on one of the higher frequencies, you frequently see a weaker signal when you enter these big stores and dense buildings, like when you enter and elevator in a hotel. If you are fairly close to a cell tower, the phone may keep it’s connection. But, if you’re starting with a marginal signal when you enter, you will likely end up with an unusable signal. I hope this gives you a clearer understanding of why you may lose signal in some buildings.