You may have to look at old bills to see if any credits were applied...in my case one monthly bill was about £14.00 (plus calls) instead of about £11, I called to enquire and was told that they applied 12 credits of £3 over 8 bills, instead of 1 credit per bill, ??? so I had had already had the years discount, I missed a trick here because they said 'would I like to renew for another 12 months for the £2.99 off E&W calls plan, I said ok but I probably could have got a further £36 off for the year £3 off line rental seems to be a standard discount to retain business, so I'll know better next time...another point was I'm on line billing so looked back to see which months I got more that one £2.99 bill credit but only the previous 6 bills can be veiwed, and they all showed one £2.99 credit,so I couldnt verify the months that this multi discount was applied !!....BT apply these things as bill credits rather that showing the line rental or call plan figure as discounted, BT recon they have had awards for their 'plain speaking' billing...thats laughable