Professional Ambulance Service

Update!
Heard back from Professional Ambulance and they were very sincerely apologetic and helpful. Because my actual ambulance ride (a year ago) was good and they’ve amended the issue that I had with the service, I’m upping this to 3 stars.
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Original Review
I was in a gnarly bike crash last May. I didn’t want an ambulance, but someone at the scene insisted on it because I had smacked my head on the road. I remember the service being fine; they showed up fast, everyone was pleasant enough, and I got from Kendall Sq. to Cambridge Hospital quickly.
The reason I sought out this profile and am writing their first review, however, is because of the terrible experience I had today with the billing department.
At the time of the accident, I was without health insurance — therefore, the bill was substantial (read: insane). But it is what it is, and I’ve been paying it back in small chunks ever since.
Without going into too much detail, the billing rep called me today to collect a late payment (my error, I fully admit) and the subsequent conversation was humiliating, belittling and totally unprofessional. I was, and am, startled and upset by the rep’s comments, despite paying off the full balance. Heck, even if I hadn’t paid them a dime, I STILL would not have deserved this shoddy treatment.
Debt weighs heavily enough, Pro EMS. We don’t need any derisive comments from you on top of it.
I know that in the kind of situations that call for an ambulance you may not have a say in which company you call but, if you do, steer far, far clear of this one. I sent them an email through their site earlier today and will update this review if they respond.