As the following: to let the caller1 to go to callee2 
Step 1: Add prefix 11 in the caller1’s Additional setting -> mapping prefix -> mapping callee rewrite rule: Initial prefix *, Destination prefix 11*, then OK ->OK ->Apply. 
Step 2: Add prefix 11 in callee2’s gateway prefix 
Step 3: Delete prefix 11 in the callee2’s Additional setting ->routing prefix ->routing callee rewrite rule: Initial prefix 11, Destination prefix blank, then OK ->OK ->Apply. 
Step 4: Add rate prefix 11 in rate group of caller1’s account 
Or you can choose not to add the rate prefix 11 int account’s rate group, you can add 11 int System paremeter SERVER_GATEWAYROUTEPREFIX, then click Apply. 