Expressvpn has one of the best 30-day money back guarantees, so if you decide it's not for you, it's easy to cancel your subscription. You can do this through the website or through the app, but the easiest way is to use your account dashboard.
First, you need to turn off your automatic payment. You can do this by logging in to the app and clicking on "Manage Subscription". Then, select "Turn off auto-renewal" and confirm. You will still be able to use the service until your billing cycle ends, but after that, you will no longer be billed.
You can also contact the customer support and ask for a refund. This is the quickest method, and they should process it within a few hours or days. However, it's not a guarantee that you will get a refund. Sometimes, they will simply cancel your subscription without giving you the money back.
It's important to note that you can only get a refund once per account, so if you have canceled it before, don't try to do it again. You will most likely be refused or banned for doing this.
If you cancel your ExpressVPN subscription, it is worth trying a different provider. There are plenty of good alternatives, including Private Internet Access and CyberGhost VPN. Both have good apps for iOS and great speed and security. They are also much cheaper than ExpressVPN. You can also choose a free VPN, but these are often less secure and have fewer servers.