Missing discount - now nice price

I had a web chat today, was offered £4.50 off broadband for 12 months back in March. (Already have line rental saver)
Noticed my last bill didn't have the discount so asked what was going on, seems I'm back on a rolling contract so the discount disappeared, thought I'd signed up to a new contract back in March.
Advisor said he could put me through to retentions to see if they could offer anything.
Explained what had happened and was offered an 18 month deal so my £15.99 package is now £6.99 for the next 18 months.
Not had any problems with Plusnet, apart from a lack of capacity a long time ago, always been very helpful if I've had any problems so signed up, bargain.