According to Lifesum's Terms & Conditions available here, you have 14 days (from the date you receive the confirmation of your subscription via email) to withdraw from the contract with Lifesum. If you consent to have access to the Lifesum services during the withdrawal period, you no longer have the right of withdraw.
Important: you need to request a refund within 14 days - no refund will be granted after that time period.
Just canceling a subscription does not automatically result in a refund, it only avoids a renewal. Please proceed as described below within 14 days in order to receive a refund. Thank you!
App Store
All payments handled by App Store, such as in-app purchases, can be refunded and approved only by Apple. To receive a refund from Apple you need to contact Apple Support within 14 days from the purchase date. To contact them, please follow this link: Apple Support or call them via a number on this page. You should receive a confirmation email from Apple Support when they receive your request. You'll receive a followup response with Apple's decision on a refund within a short period of time.
Here you can find a useful step by step tutorial on how to request a refund for an App Store purchase.
PAYPAL
If you bought the Premium membership directly via Paypal, please contact us within 14 days after the purchase and let us know which account you have bought Premium with - provided you haven't started using the app.
If you bought the Premium membership via GooglePlay, please follow these instructions by Google https://support.google.com/googleplay/answer/2479637#apps
CREDIT CARD
If you bought the Premium membership with credit card, please contact us within 14 days after the purchase and let us know which account you have bought Premium with - provided you haven't started using the app.
SAMSUNG
If you bought the Premium membership with Samsung, please contact our support with a copy of the receipt within 14 days after the purchase.