Usually on the first bill with talk unlimited 24 on it you'll have added it part way through the month so there may be calls from the start of the billing period until the date you added the plan on.
Also something to consider is that usually the total calls made & duration of these calls include ALL calls, even the free one, then the chargeable ones of these total the £5 odd.
The calls included in talk unlimited 24 are voice calls made to local numbers & those beginning with the area code 01 or 02. All other numbers like mobiles (07's), non geographic numbers (like 0845's & 0870's) or premiums (09's) are subject to the 5p connection charge as well as the standard rates. Some overseas calls are discounted under this plan, but are still subject to the same connection charge.
Hope this helps.
Dee.
