trouble installing malwarebytes

At the suggestion of an Apple support staff member, I installed a free 2-week trial of Malwarebytes when I expressed concern about malware on my MacBook Air. When the trial period expired, I took the company up on an offer to continue the protection on 3 Apple devices for $63.59 annually. I purchased the protection from the company, which apparently was a mistake, because after the purchase went through, I got a message that I could not install it on 2 of my 3 Apple devices without company support, apparently due to Apple's requirement that I purchase it from the Apple store. (This issue was not disclosed until AFTER I made the purchase). I contacted the company for support, but got no response other than an acknowledgement of my inquiry. After what I thought a reasonable time for a response passed, I contacted them again to cancel the subscription. Again, I got an acknowledgment of my inquiry, but no notice of cancellation, and the service is still on the one device I had scanned during the trial period. Anyone else experience this? If so, how was it resolved, if it was?