Samsung Galaxy S4 here. I found that my phone often switches cell towers through an app called GSM signal monitoring. I don't know if this is the phone's fault or not, but the most annoying thing about it is that when the switching happens any and all data transfer are completely interrupted and stopped, and are unable to resume even after the switching is done. This happens whether I'm mobile in a car or stationary sitting on my desk. I could be downloading 100 KBps and just completely stop and I have to restart the download all over again. Is there a way to stop this from happening? Maybe lower the tolerance on which the decision to switch is made?