spammers unknown caller

I got a call on 16-09-26, initially 1-2 calls came, then every day 2-3 calls came between 10 and 5:30, and on Sunday there were no calls. Then from Monday, 1-2 calls came, and yesterday on 25-09-26, I got 5-6 calls. Can someone tell me how long these calls will continue or if I will have to change my SIM?