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Since you remove the handset, the modem/router might be checking for a device for the incoming calls to go through.
Are you experiencing issues with your service?
You may check these articles for self help option.
No I do not have any issue with my wifi service. Recently, I have removed my local call package as I have not used it from last many months, mean my VoIP Service will be pay-as-you-go moving forward. Is it possible to completely remove this service from my package without distrupting my net service.
@dpaul1971 . The VOIP service is bundled with the internet service; it can't be removed. You've done the right thing by disconnecting the handset; no more phone calls.
@BasilDV . My router's log is full of various VOIP messages and I have my handset connected, and the messages don't correspond to getting or making a phone call. The messages either come from the residual TP-Link VOIP firmware, or TPG's own VOIP firmware or caused by TPG's VOIP server polling the router, or by people in the internet probing my router (port scan). You might ask the engineering team, or the programmers who modified the firmware, what the messages mean, just out of interest.