Thank you for contacting us and for the screenshot. The strange thing is, I don't know what the top price is for that is labeled "Unlock the power of mSecure." I have that as a note to talk to our developer about soon. If you were to open the mSecure app, however, that's the easiest way to upgrade, or you can do so on our website. If you open mSecure 6, then tap the Learn More button in the bottom of the app's menu, it will show you the upgrade price for the Premium subscription. The one you want to purchase is the one labeled "Premium Yearly Upgrade." It's $14.99 USD but only 13.49 pounds due to the exchange rate.
To be clear, that price is handled by Apple, and if you do a search to find out what $14.99 USD should be in Pounds, it's not 13.49. I don't know how they go about setting the rate they set, but that part of the process is out of our hands completely.
I just checked your account, and it's showing that you're running mSecure 6, at least one device anyhow. Can you let me know what types of devices you are running mSecure on? If I know that, then I can help point you in the right direction.