Why offer deals that are no longer available?

[#1]

When I log into my PN account I am offered a renewal deal even though my contract runs until January:

Renew today and get a fantastic deal just for you.

Fibre and line rental from £25.50

Yet when I click on the link I’m told the offer is no longer available. What’s the point in offering a special deal on my account pages if it’s not available?

[#2]

Happens a lot, the advice from staff is to call into the Retentions team and ask them about the offers. A bit off hand to me but that's what the answer given is