Really annoying call reception problem with my iPhone 7 plus

I have been iPhone 7 plus for over an year now and since last 6-8 months i have this problem where i get call drops or no reception at all which leads to difficulty in calls and as advised I have approached my network operator Vodafone and they have done everything from their and now according to them there's something wrong with my phone and so i tried using the sim in another phone and the call reception seems good in another phone; so i figure that problem is with iPhone hardware or software and apple needs to fix this as i have approached apple care and no one seems to be answering, so help me out.