we have 2911 Cisco Router and using CME IP telephony. Cisco 74XX Series , 69XX and 9971series Ip phone's are being used. PSTN SIP trunk Outgoing and incoming calls are working fine, except 9971 Series Phone.
when we try to call from 9971 series phone some network provider number its not working but if try form 74xx and 69xx series phones call can be completed.
eg: from 9971 series phone, outgoing PSTN mobile phone number 0570793163 (Service provider name is virgin mobile)- out going call is working fine
But , if i try from 9971 series phone , mobile phone number 0551183525 (Service provider name is STC mobile) call cannot be completed
But the same number , if we try from 74XX or 96xx Series phone call its working perfectly