Telephone service companies have created a special communication service without the need to use customer's equipment. It's called a "virtual number". It also has a text type of "virtual SMS center." Thanks to the virtual link you can make calls or send messages while connected to the equipment of the company.
From mobiSIP Android or iPhone: SIP Client iPhone is uniquely designed and developed to add the power of making voice over internet transfer protocol calls directly through the Android or iPhone. It’s developed by mobisnow.