I had exactly the same problem with WiFi calls (see my old posts on dropped calls). I tested my phone in another WiFi location (in a coffee shop) and didn't have problems. Even though my computer recognized the signal, my phone dropped the calls. I changed my router and verified that all phones jacks (except the router) were using DSL filters. Since then, the problem disappeared (except when I synch music).
When outside, the phone will periodically drop calls moving between WiFi and edge networks. However, I usually turn off the WiFi network anyway to conserve batteries. While at home, the WiFi connection is more reliable if I turn off the edge network so the phone stays on WiFi and doesn't look for another network. By default, I set my preferences to WiFi at home, so even if I forget to turn off the edge network, it still looks for WiFi.
