hopefully these tricks could help, i've read it from the net few weeks back when i had the same problem a you. the thing is the phone won't be able to 'dial' or 'call' any number that is not in the list from the contacts...
1. go to call settings under the 'phone' icon and set 'show my caller ID' to
everyone, try calling numbers that is not in your contact list, if it's still not working...
2. set the 'show my caller ID' to
my contacts, pull out the SIM card and put it back in. Set 'show my caller ID' back to everyone and then restart the phone.
hopefully by then the phone should behave normally afterwards, i'm going to search back where these source came from, it does help me and i guess it should help you too!
here's the site where i found out the solution
http://www.askmefast.com/My_nokia_lumia_800_is_unable_to_make_outgoing_calss-qna1849369.html
Here is the solution for that. In dailler pad,select call settings .. Select option show my caller id to .My contacts ..then press back button then dail and check ny one number in your contacts.It will be dailled. After this again come back to the caller stettings ,it will b showing everyone.again select to My contacts.after its done dont press back button again change it to the everyone.then press back button. Now tourn off your mobile ,remove your sim card.then turn on your mobile without sim card .again turn off your mobile now insert your sim card and restart it properly.. It will work.. It worked for me
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