OVERCHARGED WITHOUT ANY PROPER EXPLANATION

I'm so disappointed with Cartrack, i have been with this company for almost 14 years. So on the 13th May 2021 a new device was installed since the old one's term has expired. So Cartrack decided to deduct my account for pro rata which they say it's from the 13-31st May 2021 and they deducted my account again which they say it's for the month of June 2021. When i phoned their accounts dept today, i was told that my next debit order will be on the 15th June 2021. So i asked them, why is my account not deducted on the 1st July 2021 since the amount that was deducted already covers the whole month of June? Actually i have been overcharged by this pathetic company, i told the lady from their accounts dept that if my account can be debited on the 15th June, i would reverse the money and cancel my subscription.