Being billed an incorrect amount after cancellation

I cancelled my xfinity service over the phone and was promised that 1) the last day of my service is June 12th and 2) my bill for June will be prorated and will only reflect the 12 days of my service. But earlier today I was charged $65.67 by xfinity, which seems to be a full month's charge. I was wondering about 2 questions: 1) has xfinity really cancelled my service? 2) if so, why on earth does xfinity charge me for a full month when they promised to charge as prorated?

I would really appreciate it if anyone can answer these questions for me.

What is more ironic is that, it takes me calling twice to cancel the service. I called in May to schedule my June 12th cancellation and received an email confirmation, and when I called back to confirm my cancellation in early June, the agent said she didn't find any record for cancellation and need to reschedule it for me. I then received another email confirmation. But this overcharging still happens, which is terribly annoying.

I'm moving to a new apartment in two months and there is xfinity service there among other options, but these drama and inefficiencies has made me seriously consider not using xfinity for my new home.