Fraudulent Multiple Charges From Mental Impulse Brain App

I discovered that I have been charged for a subscription to the “Impulse – Brain Training” app even though I never knowingly agreed to a paid subscription. I only remember signing up for what I understood to be a free trial and did not consent to ongoing charges. After I realized this, I cancelled the subscription, yet I noticed that I have still been charged. From my point of view these charges are unauthorized, as I did not clearly consent to a paid plan and I acted to cancel once I became aware of it. I request that all charges related to this Impulse subscription be fully refunded and that my subscription be completely cancelled so that no further payments are taken. I want clear confirmation that all past and future charges will be removed; if this is not provided and my money is not reimbursed, I will consider taking legal action. I expect a prompt response and resolution.