Stamps.com Three Calls to Cancell and Monthly Charges Still Appear California

I intially signed up at Stamps.com, thinking it would save purchasing postage.  However, I found the software, the special print paper, the "membership' costs to be out of range for the quantity used for home.  $22.00+ a month for a few letters mailed each month.  I forgot about the account for over a year, then called them.  The first call resulted in a modified plan (to which I did not agree, but the 'Customer Service' representative entered on my behalf after hanging up), and when I noticed an immediate charge for a lesser amount, immediately called Stamps.com back, told them I had asked to cancel all accounts; the woman seemed to sympathize, and said the plan had been terminated.  My credit card showed small chargebacks ($5.00) presumably for overcharging, and then this month, there it was again:  $15.99 for another month of postage subscription 'services' from a company who had been told twice to stop all charges.  When asked why I was terminating, because three letters a month doesn't justify $15.99 for subscription, plus $20-something for special postage paper, and I had been subscribing for over a year and don't know that I used them even once.  Today, the third call, I had to state "I do not want any service from Stamps. com in any shape or form, I want this account CLOSED, with no further charges and I want a refund for the last month as I've already called TWICE to end these recurring charges."  Hopefully they will do it this time.  They have sent a confirimation email, which I will keep in case it shows up again in future months.  Ishould point out that there were months where the Stamps.com charge did not appear (after I closed the account previously) and then it suddenly reappeared on my credit card a few months later.  WATCH THESE PEOPLE CLOSELY.