About 15 years ago the company I worked for was making a call detection device for prisons. So we wanted to detect the inmates making phone calls. They obviously shouldn't have access to phones. With 2G this was possible with a simple antenna, and a envelope detector, at the beginning of the call, the phone transmits at max power to determine how much power to use. Measure RSSI and then reduce the TX power to keep acceptable link budget.
With LTE it's a whole different issue. Browsing the web isn't different from a phone call, it's all data. It's not impossible, but I don't think you will have access to the software to do it. Or if you do, then you already know how to do it, and you wouldn't ask it on a forum.