why aren't there bond exchanges where the posted bid and ask represent a firm commitment that actually fills when you hit it? Why are the broker fees for trading bonds so damn high? The general plumbing for bond trading seems many decades behind equities.
What a secretive OP. You must be trading some strange/unknown/illiquid bonds from don'tknowwhat Exchange from don'tknowwhat broker. Also no one knows whether you are trading US or Syria or Russia or Venezuela ...Treasuries, corporate bonds mortgage bonds ... Try trading popular bonds like ZB ZN BUND BUXL BTP SCHATZ GILT ... As to which broker to use, you can try contacting the broker cum ET sponsor
because nearly 100% of the trades are executed otc and among institutions, do you have few millions commitment to buy or sell? you can go to cme to trade bond futures, that is first come first serve.