misdiagnosed repair what to do ??

[82XD393.3v]

Hi im after some advice on how to go about recouping some of the money i was charged for a repair that wasn't nessary
I broke down a couple of weeks ago in a diesel transit van took to my normal mechanic but he didn't have the tools or diagnostic equipment to find the problem he spoke to a guy who works on tranists and he advise it take it to a diesel injection and fuel specialist which i did
first day they ran a scan diagnostic machine which gave them no errors,the following day i was told my high pressure injector pump was shot and need to be overhauled so i had the work done at a cost of $3300 of which $1770 was labour and the rest parts after 5working days i got my van back and as i use this as my income i also lost $1200 in income
About 2 to 3 days after it started to show the signs of the problem reoccuring
(trouble starting) till about 6 days it stopped again and i couldn't get it going (identical symptoms and breakdown)i got it towed to the repairer they did a scan again and nothing was told maybe the injector pump is gone again nexted day got a call your vans ready turns out the drain plug on the fuel pump had a small leak so it was drawing in air which inturn air locked the injector pump
Picked it up walked in the receptionist saw me coming and quickly grab me keys and invoice and handed it to me without a word and retreated into her office before i could say anything
So the problem was a $60dollar fuel filter all along and the obviously knew they where in the wrong but instead of appoligising to me and offering at least the labour charges back i got ignored what can i do???
$3300 on unessary repare plus 1700 in lost income