How to call from the outside to the internal number of a SIP operator, for example gigaset.net?

Question

SIP

There is a home voip Siemens Gigaset A580 IP. Two SIP providers gigaset.net and bestvoipreselling (one of the DELLMONT SARL crowd) are configured. There is no connection to a regular wired telephone line. I would like to call from outside, ie. from a mobile phone, to home handsets tied to the aforementioned base. Is there any way to call existing sip accounts without paying for an external phone number?

Answer 1

Well, it all comes down to installing a sip client on the mobile phone...