See this Apple article:
Request a refund for apps or content that you bought from Apple.
Request a refund for apps or content you've bought from Apple – Apple Support (UK)
If you want to cancel a subscription from Apple
If you want to cancel a subscription from Apple - Apple Support
If the subscription that you want to cancel is not listed
If the subscription that you want to cancel is not listed – Apple Support (UK)
If you see "apple.com/bill" on your billing statement
If you see "apple.com/bill" on your billing statement – Apple Support (UK)
If you have requested a refund, you must wait until Apple has approved. Then you will receive a message from Apple.
Refunds are not guaranteed. For more information, see the Terms & Conditions.
Click here for more support and assistance.
See also:
iTranslate app -> Auto Renewable Subscription Terms:
Subscriptions are billed monthly or annually at the rate selected depending on the subscription plan.
The price corresponds to the same price segment, which are set in the "Apple's App Store Matrix" for other currencies.
* Your free trial subscription will automatically renew to a paid subscription unless auto-renew is turned off at least 24 hours before the end of the free trial period.
* Please note: any unused portion of a free trial period (if offered) will be forfeited when you purchase a premium subscription during the free trial period.
* You can cancel a free trial or subscription anytime by turning off auto-renewal through your iTunes account settings. This must be done 24 hours before the end of a free trial or subscription period to avoid being charged. The cancellation will take effect the day after the last day of the current subscription period, and you will be downgraded to the free service.
* Account will be charged for renewal within 24-hours prior to the end of the current period, and identify the cost of the renewal.