stamps.com Continued billing after I requested cancellation - for TWO YEARS!

I signed up for a free trial at stamps.com two years ago, which required giving them my credit card info. Within the trial period, I called them to request cancellation of the trial.

However, unbeknownst to me, I was still billed over the next two years for access to the stamps.com website. I received no actual services and made no actual purchases; indeed, I literally did not log into the website a single time in all that time.

In total, stamps.com collected about $250 in account fees from me while rendering literally no service whatsoever.

When I recently realized what was happening, I contacted their customer service. They offered me about $45. I explained that that was not nearly sufficient, so they moved me up to the next tier of their customer service. After failing to reach me by phone (I had moved while my account was active), they emailed me a template letter. I replied requesting email communication. When my replied went ignored for more than a week, I emailed again, this time receiving a reply.

I was told (for the second time, "We have carefully reviewed your account history and have found the service fees that were applied are in accordance with the Service Agreement to which you agreed."

In other words, "We're going to keep your money because we can." Never mind that I never received services or products of any kind.

When I protested that this behavior was highly unethical, they "issued a courtesy refund of $111.93." 

Therefore, as of now, stamps.com has 'only' dishonestly kept about $138 of my money, having reluctantly returned the rest.