In case you are in an area with bad coverage we can do very little.
Nevertheless, in most cases there is a solution.
Step 1: Put your phone in flight mode.
Step 2: restart your phone and turn off the flight mode.
Step 3: If it still does not connect, try to select a mobile network manually.
If the above does not help, please write us using the contact us page and we will troubleshoot with the mobile carrier and provide you a solution so you could continue your activities.