With some phones and devices a small change to your settings is needed to activate touchtone dialling.
To test your VoIP phone's configuration dial 10020.
If your device is listed in our Setup Guides menu, please first check your settings against the setup guide.

Your VoIP phone must support DTMF tones via RFC2833.

In your Aastra phones web settings under 'Advanced' --­­> sipgate 'Line' ­­--> 'RTP Settings' please check that the 'DTMF Method' is set to 'RTP'.

In your sip.conf for the peer sipgate line please change 'dtmfmode' from 'info' to 'rfc2833'.
Draytek Vigor:
In the configuration interface of your router please open 'VoIP' ­--> 'Phone Settings' --­­> and select the sigpate 'Index'. 
Next click 'Advanced' and set 'DTMF Mode' to 'Outband (RFC2833)' and the 'Payload type ' to 101. 

Please set 'Send DTMF' to 'via RTP (RFC2833)' and 'DTMF Payload Type' to 101

For Grandstream GXP- deskphones, the DTMF option will be found in the 'Account' settings.

Siemens Gigaset devices:
For most Gigasets, in the Web Configurator menu under 'Telephony' --­­> 'Advanced Settings' --­­> 'DTMF over VoIP Connections' please set the option 'Send Settings' to 'RFC 2833'.
In your Snom's Web User Interface under 'Setup' select your sipgate 'Identity' and then click the 'SIP' tab. The option 'DTMF via SIP INFO' should be set to 'Off'.
In the 'Advanced' settings of your Yealink's sipgate 'Account' please set the 'DTMF Type' to 'RFC2833' and the 'Payload Type' to 101.
Cisco SPA: 
In your Cisco SPA device's Line or EXT settings check that 'DTMF Tx Method' is set to 'Auto' and 'DTMF Tx Volume for AVT Packet' is set to: 99999999