These follow our step-by-step guide
1. Tap Menu, and then click "Settings"
2. In the section "links" tap "Mobile Networks"
3. In the next submenu it comes to "network mode", where you now have the following options are offered:
LTE / WCDMA / GSM (connect automatically)
WCDMA / GSM (connect automatically)
Only WCDMA
Only GSM
Now selects "GSM only" from, so that connects your Samsung Galaxy S6 EdgePlus only with the GSM mobile network. This results in a rule immediately in an improved signal strength and voice quality in telephony.