You'll have to call customer care about cancelling the Rs. 149 plan. I don't think they'll allow it. I've read on the Jiocare site that if you have recharged with Rs. 149 and also done the Prime recharge, then you should recharge for Rs. 303 and higher, and then you'll get the Summer Surprise scheme wherein you'll get three months free, after which in the fourth month, the Rs. 303 recharge will become effective, and in the fifth month, the Rs. 149 recharge will become effective.
Summer Surprise can be activated on any number if you do the Prime recharge and a Rs. 303 or higher recharge. Then you'll get three months free, plus the Rs. 303 recharge or higher in the fourth month, and any other recharge that you have done previously in the next month.
I also have three SIMs, and I've started doing the Prime and 303 recharge on them using Jio Money, wherein I get Rs. 50 cashback with each recharge.