A free trial can only be purchased ONCE per Apple/Google ID as per their terms.
We have no way to detect if your Apple/Google ID has already bought a Free trial. The payment dialog to confirm payment comes directly from Apple/Google and clearly states if a free trial is eligible and the price of the product.
Please ensure you read this correctly before confirming the purchase - we cannot be held responsible for this being overlooked.
Note a trial subscription must be cancelled upto 24 hours before it expires in order to not be charged/renewed.
Apple/Google handle all payments/refunds and subscriptions, not muzmatch. Only a customer can cancel a subscription - we are not able to ourselves.
Please refer to our other answered questions regarding cancelling any subscription as well as applying to Apple/Google for a refund.