Subscription fees of Rs 50/month for Coin will be applicable only if you buy direct mutual funds on https://coin.zerodha.com/. There are no charges if you are buying or already hold regular plan mutual funds.
Even the Rs 50/month fees will be applicable only after the first Rs 25000 of direct investments done on coin. You can track the value/worth of transaction executed on coin dashboard itself.
Note that this first Rs 25000 without the monthly Rs 50 as subscription fees is just one time and not yearly.
To cancel your subscription, once you have exited all the direct mutual funds, you will have to click the deactivate button as shown below.
Also, check this link which explains how much more you can save by investing on Coin - our direct mutual fund platform.