Your Singa Premium trial period lasts 30 days, after which you will be charged the basic price for Singa Premium unless you cancel the subscription at least 24 hours before. Here are possible reasons for a charge at the start of a trial:
The trial period was no longer available
If you have previously used a free trial with the same Apple ID or Google account, you cannot use it again. In this case, your subscription will start immediately as a paid one.
You accidentally selected a paid subscription
It is possible that you directly selected a paid subscription instead of a trial (they can look quite similar).
The app store did not offer a trial
The App Store or Google Play do not always offer a trial to all users (for example, due to previous usage, region, or promotion).
This may be a pre-authorization
Sometimes a pre-authorization is placed on the payment first, which looks like a charge, but is not a final payment.
You already have an active subscription
If you already have Premium (or had one before), your new subscription will not include a trial period.
Previous subscription is affected
If you have previously subscribed to Premium and canceled it, you may no longer be eligible for a new trial.
Rare technical error
In some rare cases, the trial period does not activate correctly, even though it should. In these kind of situations, contact our support at support@singa.com for clarification.