Google has been making some updates to their AdWords policies, and starting from this month, will no longer be allowing telephone numbers in the ad text.
Any ads which contain phone numbers in the text, will be disapproved by Google. If you do still want to include a number with your ad, the call extension feature is available.
There are advantages to using the call extension feature, as you will easily be able to measure conversions from your ads and track information such as, phone impressions, phone calls, phone-through rate and average cost per call.