Legal Notice

There is a fight between me and my relatives over a loan which was given by me to them on 2016 via NEFT bank transfer. Today I was about to receive legal notice from them via registered post but I asked postmaster to keep it in post office. He obliged and told me post office holding period is till 7 days. I am pretty sure legal notice relates to the loan. My question is whether I can goto police station and register the complaint. If yes, then how should I deal with legal notice.