Until recently, none of the phones in the Siemens Gigaset range supported TLS for SIP, the technology you need to encrypt VoIP calls. However, Siemens have now recently a new Gigaset range that DOES allow TLS on their phones:
DE310 IP Desk Phone
DE410 IP Desk Phone
DE700 IP Desk Phone
DE900 IP Desk Phone
Please remember that encryption needs to be active at each end of a call (Yay.com and your device) to work.
If the model you have isn't listed above, then unfortunately that model doesn't support TLS for SIP.
Check out our VoIP Phone Store for a wider range of other devices that do offer full TLS for SIP support.
If you need any further help today, please don't hesitate to contact our friendly support team on 917 900 1929 or by email!