I had a similar issue earlier in the year with line rental saver. I've paid the £120/year for some time and was told this offer would continue to this year - all I had to do was call in (the agent even put a note saying so on my notes).
When I phoned as agreed I was told no deal. As Sky had a 50% off for 12 months offer running I just gave VM my 30 days notice (didn't want to move to Sky as Mrs G doesn't like the colour of the Sky guide
).
A few days later VM called to see what they could do to make me stay, I suggested keeping their promises would be an idea so she did the line rental for £120 and put a monthly credit to cancel the price rise and reduce the price (without me asking). She also put another note on the account to say the line rental saver would continue at £120 for another year.
I had to agree another 12 month contract but was happy with that. Our package is:
1terabyte TiVo
500 gigabyte TiVo
XL TV
Talk unlimited
Caller display
£5 08 calls
200 Mbps internet
Basic price £67.99, we get two loyalty discounts of £3 and £11 so pay £53.99 (plus line rental saver at £10/month).
I didn't enjoy threatening to leave but a promise should be kept.
Cheers
Grim