Can't call out or receive call after drop in water

Dear iFixit community, I have an iPhone 5 white 64 GB. Sadly, it had an accidentally bath in a lake. Not salt water. So it has dried up. It power up and down fine, WiFi works and so on. But for some reason, I can't call out or receive calls. I have done the following: 1. backup the device via iTunes 2. checked for updates and updated with the latest 8.3 iOS and the update about cell network provider (I think is the translation) 3. changed the SIM-card. 4. Factory reset. After that, I managed to do one call out and one incoming call. But then it died again. After these one-timer, the ability of making a call and receive a call stop working. All other function are working fine, like web-surfing, take mail via WiFi, get updates via WiFi.

So given that, any thoughts of what can be done? Can I maybe replace the SIM-card reader?

Kind regards

Leopold, Sweden