what to do about dishonest broking?

I have been zapped by a well-known broker (a major online institution).

I had a small trade first in line on Monday, I was joined by one other on Tuesday.

Wednesday morning the quantity I had on sale was surpassed, but I had only 1,300 sold.

I took note of the entire proceedings. The other person's trade went through 5,300 and 8510 until all were sold. I rang to query and they really had no excuse. The dealers claimed they hadn't seen this before.

I am sitting with 2890 to be sold. The order for 1 after me has been removed.

I asked that the first 5,300 receive a deduction enabling my order to be filled. Claim they can't do that. I don't believe that.

If they haven't seen this before???? then it's either a racket or a trading platform error...and a platform error is much worse.

To whom do I take this situation please?

(They have promised me I'll be paid out for the remainder of my order if it doesn't get filled)....when? I'm waiting on another call so they can give me a no excuse lame excuse.

I used to work for the group (about twelve years) and was in software development in the IT and Business areas for that time.

Thanks,

I think this is serious enough to make a wave about.

If we can't trust a major broker? In these times people are desperate and they'll do anything. This would cause a major scandal and this action is a huge business risk.