chris barnes

I have been advised by hmrc that I can increase my NI contributions above the required 30 years in order to improve my reduced state pension , am still waiting for a letter giving details and confirmation , however have been advised that this is taking at least 6 months ,this would then be after the deadline date of april 2025 so what would be the implications?
Also I already have 35 years contributions so why cant they use the 5 years in the calculation against the old rules pension where it only requires the 30 years ,rather than me paying for extra years