I assume you are in the UK.
How long have you worked for the employer? If it is less than two years, I don't think you can do very much.
ACAS
https://www.acas.org.uk/ is a very useful site for information regarding HR matters.
I know it can be hard, but you need to keep the communication channels open.
Lastly, I dislike the term "I was let go", It is becoming more and more used, and for me it means allowed to leave. You were dismissed.