Please help - Two CoS - Two jobs

[Charmeire]

I had accepted a Job at one hospital and they had assigned COS oon my name but then I accepted another job and asked them to withdraw their RCOS but when ever my new employer tried to assign RCOS on my name, it says that Unused RCOS already exists for the migrant and rCoS can't be assigned. I have tried asking my previous employer but they said they even got the mail from UKVI stating my application has been returned. My new employer now wants to withdraw my offer of employment. I don't understand who to contact. I tried mailing UKVI but they say my sponsors should talk to them and my sponsors say there's nothing they can do. I am in big fix.