Spud Spud64

I worked overseas during the 06/16 period and work and paid NI in the UK up to that period and had 30 years NI. I am now back in the UK and due to receive my state pension in 2025. I completed a CF83 form and received a grid with the amount at class 2 National insurance that I could pay to fill gaps in my record for while I was overseas. As requested I contacted the relevant department to check that I could pay these gaps and increase my state pension and was told the amount my pension would increase by. I duly paid the relevant amount for two gap years. After recently hearing a number of people saying you are not allowed to do this I am concerned that I have wasted my money. Does anyone know if you can still pay gaps if you have 30 years by 2016.