Testora IQ Charged £39.98 Instead Of £1.99

I recently used the Testora IQ app and selected what was advertised as a one-time test for £1.99. However, instead of only being charged £1.99, I was unexpectedly charged £39.98 for a subscription that I did not knowingly order or authorize. The purchase was made on 21/03 via Google Play. I did not agree to any recurring subscription and was not clearly informed that a £39.98 subscription would be started. This charge came as a surprise, and I consider it unauthorized. I kindly request that the unwanted subscription be cancelled immediately and that the £39.98 be fully refunded to my account. I also ask for written confirmation that the subscription has been cancelled and that no further charges will be taken.