Is Line Rental Saver payment by card only?

[#1]

Just paid annual line rental saver and it's increased by £48. An almost 35 % rise. I was lucky in the past in that I could pay it just before the price rise but not this year and been hit with two years worth of rises.
However I could not find a way to pay by direct debit and had to use a credit card. Is there any way I could have added it my next month's direct debit or is a card the only way to pay? I ask as my current account gives 3% cash back on my home phone and broadband packages direct debit payments.

[#2]

I've had a search of the PN website and can't find any reference to payment methods for LRS.
Possibly you could take a punt and try "chat" to ask the question?
Edit to add, my LRS expires on 31 Dec. and I've just gone through a "dummy" renewal. In spite of this
"Please note that Direct Debit payments take 5-7 working days to progress.
If your payment isn't received within 14 days of your billing date, your browsing will be restricted and you'll be charged a fixed fee of £5.76. Pay by card today for a faster payment."
The only option available was to pay using an existing credit/debit card or add a new card. There was no Direct Debit option in spite of the quoted text above which seems to only refer to browsing and not telephone service.

[#3]

afaik it's card payment only.

[#4]

Thanks for the replies.
Like Newagetraveller I saw "Please note that Direct Debit payments take 5-7 working days to progress " and hoped that they had changed from last year but obviously not. £5.50 cash back would have been welcome as to quote an advert "Every little helps". The first time that I took out line rental saver in Dec 2011 it was added to my bill but haven't  been able to do that since.

[#5]

Unfortunately LRS payments are card only.
Apologies for any confusion caused by the notice regarding the time scale for direct debit payments, I believe this just comes up because you are sent to a payment screen.