Voipfone Webcall feature, Pause?

Hi, I am trying to make calls from my university phone system by using the
web call feature, which calls you and the recipient.

The problem is that to get through to my room, you have to dial an extension
after the call is answered. When calling from an ordinary or mobile phone
this can be achieved by putting a p in, which pasues before sending the
extension digits.

I just tried this twice with voipfone and while it didn't give an error, it
also didn't call me.

I realise with many voip systems like the sipura, it is not possible to send
digits after a pause (atleast not when connected to pstn). Perhaps this is a
technical limitation voipfone are up against too?

I have emailed their tech support, I'll let you know what happens.

Mark