How acurate are phone call timers

Posted by Nitro Fan
Are there any readers out there who are technically qualified to answer a question for me please.
A: How accurate are the outgoing time call timers on Sony Ericsson Phones,
B: Are there any types of out going calls they do not log? Vodafone are trying to tell me that phone call timers do not time or log all calls, ie 191 & 242.
This statement seems to be total rubbish to me I have just rung 242 and my call timer has clocked up the exact duration of the call and added it to my running total any help & advice gratefully accepted.

Posted by Jowi
call timers starts once the recpnt answers the line. its acurate.