Discounted line rental. Still not applied!

[#1]

Hi
Signed up back in January for PlusNet home phone and raised the required ticket a the time to get the first 3 months @ £0.99p but this wasn't applied. Raised another ticket and was told it would be applied to the next 3 months.
Quote~
We are pleased to be able to inform you that a member of our Customer Support
Centre has now escalated your Question [number  27960030 ]
for further investigation.
The following comment was added to the Question
Thank you for your query, it looks like when the account was changed back in Jan the discount was removed for some reason. Please accept our apologies for this and I have added the discounts onto your account for the next 3 months.
Kind regards,
Customer Services Agent
~end quote
I've just checked again and I'm still being charged £9.75. Can someone please escalate this for me as I don't want to raise yet another ticket and find out nothing happens again.
Thank you
Sean
adie:red removed csa full name as per link:rules]

[#2]

Hi Sean,
Looking at your latest invoice I can see there was a discount of £8 applied against it, there's also 2 further discounts of £8 that will be applied on your next 2 billing dates.
Cheers,

[#3]

Thanks... I'll have to take your word for it as I just can't see it on my bill. I just checked again in case I'd missed it but no credit shows up.
Cheers.

[#4]

You need to look at your invoices, not the phone bill. Are you looking there?