How much does One Scream cost?
One Scream costs £1.49 a month, or save almost 20% by signing up for a £14.49 yearly subscription.
I am having trouble paying
Please click on this link for simple instructions from Apple on how to change or update your payment method https://support.apple.com/en-gb/HT201266
Android users can browse Google’s support and pay section, https://support.google.com/googleplay/answer/1267137?hl=en-GB
Are there any hidden extra fees, for example when I have created an alert?
There are no hidden fees, what you see is what you get.