AMC + popped up on my screen could not delete it on tv, next I know I am being charged for it.
1. never signed up for the channel.
2. how did they get my account information? the only service I had paid for was HULU years ago.
3. now I feel I have to change bank accounts to avoid future charges.
very poor way of doing business
I'm just guessing, but AMC+ was probably being advertised either on a screensaver or on the Home Screen and you inadvertently pressed a button that installed it. However, that shouldn't have started a subscription. You can cancel the subscription by logging into your Roku account at https://my.roku.com using the email address that's displayed on your Roku device under Settings->System->About and then try Account/Billing support at https://support.roku.com/contactus to try to get a refund.
While you're in your account at https://my.roku.com I strongly urge you to add a PIN to your account so that channels can't be added and purchases can't be made without entering it.