I'm looking for software/app which provides service for two-way communication (text and voice calls) to use as replacement for my mobile, so I can communicate with people who has mobile phones, but I don't have (so my full interaction is on OS X). So something similar to online fax services, but two-way for texting and calling.
I can't use Messages/Facetime, since it's bound to my mobile, so people not having iMessage support, I can't read the messages online, but are sent to associated mobile instead.
I can't use Skype, since they're offering only registration of landline numbers so they doesn't support texting. Secondly I could receive incoming call to registered number, but all outgoing are shown as my mobile phone, so when they call back to that number, I won't receive it on Skype. And when I'm trying to verify my Skype number (so it can show as outgoing), it doesn't let me, as it says Invalid phone number (probably because it's a landline).
I can't use WhatsApp Messenger, since it doesn't provide its own number or I can't use two-way communication with people who doesn't have WhatsApp.
Mainly I'm looking for support for UK mobile networks, but support for international numbers would be great.