Get them to supply you a replacement handset. They have proven that a T Modem and T voice are dropping communication to eath other, otherwise they could not have fixed it. One is at fault. If it was a T Modem on a Telstra phone line and your internet kept dying they would replace line or modem, so its no difference. You can always return it if problem stays, then they do the modem if no fix.

I just returned mine to Telstra for full refund. I'd had the phone for almost 3 months. Buy one with a remote base station that plugs into the back of the router/modem but allows the phones to be placed anywhere.

I have bought a T-Voice 503 which I have not been able to pair with a Telstra Smart Modem Gen 2. However, having read through dozens of comments on the Telstra Crowdsupport website it seems that the problem is likely not to be the handset but the modem. There are many reports of the dropping of connections being corrected by modem firmware updates. When reporting problems with pairing or dropping of the connection it is important to say which modem is being used.

They can, well sort of. If its the phone book it can be set as local or base contacts which is shared among all phones.

Yes, had the exact same experience but the Quick start guide say to press "register" then press the pair button. Should be the opposite ! Press pair first for 5 seconds then register, then it works. A technical support person could not explain to me what no base meant either !!