Mobile Internet connection topic

Hi, sorry for disturbing, I have a weird connection problem and I am pretty sure it is not the internal antenna... When i use the phone for Internet, mail etc etc.... Everything goes fine it uses a 4G connexion and I almost never have a problem, I do have a problem Sometimes when I am not in a 4G covered area... Than i have to change the network modus to wcdma /gsm automatic because if I leave it on lte /wcdma /gsm the phone is jumping all the time between hspda /h/edge gprs... And this goes fast like that that connection fail... This problem stops when i change modus than I get a stable 3g connection.... A little bit disturbing but Okay..... The biggest problem is that I m always connected with my messenger services like for example WhatsApp.... When i have the phone in my hand no problem at all.... But when he stays on the table or in my pocket it is kinda weird.... Sometimes I don't recieve my messages and than suddenly when I pick up my phone I get like ten messages in once starting from like half hour before.... All this started like three weeks ago, network provider say there are no network problems, I didn't drop my phone or something... Internet connection is just acting very strange lately and this started before I updated to the official 4.4 rom and didn t change after...... I also have to tell that I don’t have problems at all with phone calls or texts messages..... It's just those two mobile Internet issues.... Since i m only good for using the phone and don't know nothing about the technical parts or something... I wanted to ask the question to all of you experts.... And wanted to ask for help and if possible a solution? I want to thank you in advance and hope you guys can help me soon.... Kind regards...

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