When I change network in Samsung Galaxy S5 high copy to GSM/WCDMA (auto mode ) it stay in GSM only. What can i Do ??
follow Susendeep.D suggestion, also try to switch off airplane mode. You can also call your carrier they will send you configuration text vie email, you have just to click on it.
Firstly,make sure that you are connected to your original carrier and not other one which is providing you roaming service.Then turn off data by unticking 'Data Enabled'.Then try switching to wcdma network.
If this doesn't works,then it might be the case that your SIM card is older and you need to use a new one.