NRAM overcharged interest on mortgage

[Lara B]

Hi all, was hoping to get some advice from anyone who may have been overcharged interest on their mortgage with NRAM. We were contacted by NRAM at our new address as we had sold our property and moved our family after battling to keep up with mortgage payments when the fixed interest period ended. We were being charged too much interest on our repayment mortgage but were not aware of this at the time, the additional monthly payments eventually led to arrears culminating in being threatened to repossess our property through court, we took the situation into our own hands and sold our family home of 23 years. NRAM after 3 years tracked us down to offer redress for overcharged us, we were told they applied higher interest rate when we ran into arrears which they admit was wrong therefore they would like to issue a redress cheque. My question is do we have grounds to seek legal action for the error they made?