Salams Premium subscriptions are billed and managed through the Apple App Store and Google Play Store. Please find instructions on how to cancel an iOS or Android subscription:
If you're an iOS user, follow the cancellation instructions here - https://support.apple.com/en-us/HT202039
If you're an Android user, follow the cancellation instructions here - https://support.google.com/googleplay/answer/7018481?hl=en