If you use the VPN for occasional simple webbrowsing, emails and other low-bandwidth uses, then PayAsYouGo can be a great option.
Not recommended if you watch a lot of TV/video/Youtube etc over the VPN because this can quickly use up all the GBs (choose Unlimited or Subscription instead).
With a pre-paid PayAsYouGo account you can spread it over a whole year so your monthly cost becomes really low, and you can always reload with more GB's if necessary.
Pre-paid 10, 60 or 120 GB transfer
Pay only for what you use
Connect up to 10 devices simultaneously
Use for up to 1 year
Freely change between all VPN servers in all countries
3 Months Full Satisfaction Money Back Guarantee
Free native Android app included (100% Made in Denmark in-house)
Spend your GBytes whenever and however you please but your account
expires either when your bytes run out or after 1 year. You can then
renew it or buy a new account.