Texted In WhatsApp Group That I'm Leaving This Job due to extra Workload

Hi, I have joined a company on 20 April , after that they asked me to Upgrade my Internet Plan and gave us training for 20 days without any leave and compensation. On 28th April they sent me offer letter and started my work. First they said that I have to work 10 hours but later started giving target which i cannot complete in 10 hours, it was taking me more than 12 hours to complete. I told them that it's increasing working hours but no they kept increasing target day by day. Now it was taking me 12 hours of work to complete daily target. After 11 days of work i got frustrated i told in work WhatsApp group that offer letter says only 9 hours but you are giving us target which one can complete only in 11-12 hours, and told them that i will quit this job now i will also file a case against them. But now HR is saying that what you did was against our policies and this will lead to legal action against me. Now my question what she can do and what i can do in my defense if something bad happens ? Thanks