I have mixed views about this.
On the one hand, if you by your own admition can be a pita to work with then you know this is a wake-up call and you need to think about what you can do to improve.
otoh if these people have been pretending to be your friend, have been organizing a night out for you and all the while bitching about how glad they're going to be when you leave then really they're not exactly such lovely people themselves are they?
I had a similar experience when I worked for a large organization although it didn't involve going through anyone's mobile phone
Part of this company's performance review process (and you had a review every three months) was for your team to provide feedback on what they thought of you as a person. It went far beyond the boundaries of how you did your job and entered into the relms of personal opinions - honestly, the school playground pales into insignificance
by comparison.
So anyway, I worked in a team of about eighteen people, all of whom I got on with very well (so I thought). We didn't have a massive out-of-work friendship happening but we seemed to have a bit of office banter, occasionally went to lunch, etc.
And so came the time for my performance review, and after having had my review in which my performance in my job was graded as excellent, so came the time for my team's feedback to be presented to me. And I was absolutely ripped to pieces. All on paper and with peoples' names signed on the bottom.
I can't remember exactly what was said but it was all horrible. I was good at my job (according to all of them without exception), but not a nice person, not wanted in any of their conversations, and so it went on, page after page of it.
I had good feedback from two of my colleagues, and from all of the teams I worked for,
I was totally devastated and never saw any of them in the same light again. But i worked for the company for another 2.5 years before I was able to leave.
Tbh I think most people do a bit of bitching. I think that some can just be more two-faced than others.