iPhone 7 connectivity issues (cannot maintain a call, showing no service, data/GPS problems)

After having my iPhone 7 for almost a year I am having connectivity issues. I can no longer keep a call. I can have 15-20 drops within an hour. Also, DATA/GPS turns off and on. I am in well populated areas where service has been fine before. This doesn't appear to be a carrier issue as other people with the same carrier do not have problems.

How is this fixed. What's the purpose of the phone if you always need wifi to use it.