I work for various marketing agencies. The various agencies get different contracts from different clients who want their products promoted. Most agencies give only a few hours of work each week, so it's common to work for more than one agency at a time.
There is one agency I've been working with for about a year. For convenience call them Promote Me. At first the agreement was to get paid incrementally more after working a fixed number of shifts. The pay started at $x/hr and got increased to a maximum of $y/hr. One day I got an email from upper management. With minimal paraphrasing, the email said
We have more more of the type you have been doing and it's in your area. If you are interested in a new contract at $x/hr please reply back to this email. If you're not interested please return all company property.
$x/hr is substantially less than what I had been making, however they have work on days most other agencies don't and I thought it wouldn't hurt to still be on their roster.
I replied back to this email saying I was interested. They just kept giving me more work as normal. The job is very independent but on a few occasions I worked with someone else from Promote Me. They all mentioned how they are getting paid $y/hr (which was what I was getting paid before the "new contract"). I checked with my manager if there was some kind of mistake and his reply was basically "you're getting $x/hr, here's the email where you agreed". I assumed my colleagues were mistaking or bluffing but the other day I was working with one who showed me the invoice on his phone. This confirmed he was making $y/hr.
My manager was recently replaced. I've had some issues with the new one. I've asked her 4 times for an explanation why I'm getting paid less than everyone else and what I can do to get a raise. She has ignored all my messages on the subject (but has replied to others). Once when I was speaking with her on the phone about something else, at the end I brought up the subject and she said I had to book an appointment to talk to her about it. I didn't really know how to reply but when I messaged her asking when is a good time for a meeting about it, she ignored the message too.
It's fair that I did agree to $x/hr but I didn't know everyone else was getting paid the old amount which was higher.
I have checked with 5 people though I didn't believe it until one showed me his invoice. I know some getting paid more have worked for the agency a shorter period of time than me. We have exactly the same job and duties. I think it's a bit odd to talk about wages but it's always been the other person who has brought it up. $y/hr is higher than the average industry standard and $x/hr is lower than the average.
Any advice on what I should do? How should I react when a colleague starts boasting how much they make? Should I continue trying to follow up with my new manager or contact her managers? My new manager has simply ignored other messages too and I don't know how to react to this.