Linkus Mobile via GSM Line

I want a option to change the communication channel from Linkus Mobile to PBX from Voip/Data to GSM Line call. Other PBX has such a feature. With the Feature i can use the Linkus Mobile Client all the time. At the Moment i can´t use it because the Mobile Data Network is not good and local provider block or destroy voip traffic over mobile data. So using Linkus mobile sucks. That feature is a massive improvement! I think it is easy to build the feature with asterisk DISA.