You'll need to cancel that subscription/recurring payment via Account Settings > Payment > Manage Automatic Payments > Merchant > Cancel
Then resubscribe with different amount at merchant website. You can also check with the merchant to see if they can change it from their end or through your online account with merchant first.
I spent a lot of time following various instructions on different phones and computers. There is no way to change the amount of monthly recurring payments through paypal that I could find. Finally, I went to the merchant's website and set up the new payments through them. Their site made the changes to PayPal once you authorize it. I then signed out of paypal waited a few minutes and signed back in. I went to the automatic payments section and found there were now two separate payments set up for the same business. I simply found the one I wanted to change and cancelled it. This might not work for everyone, but I hope it will save some from a headache. Good luck.
