You can say just say: I can't hear you (clearly). Perhaps there is something wrong with the line/Perhaps we have a bad connection/and so on. Hope this helps :)

We lost our connection. The connection was lost. We were disconnected. We lost contact. I lost you. The call must have been dropped. WIFI went out between us. We had technical difficulties and lost contact/connection. Our internet is really laggy at the moment. Our internet may have cut in and out. The Wi-Fi signal must have gone out.

We have a bad connection. We're losing our connection. We lost our signal.

Incorrect.

I am here for you Irena