What can I do after wrongful termination without prior notice?

My scope of work increased from the date of joining. So, when the March increment cycle was about to happen, I had a meeting with HR to discuss it and reflect the same in my compensation. However, I was hired four days after the March increment cycle began. I followed up with HR, and they said they were considering my case. My manager then told me to wait for three days for a meeting. After that, I stopped taking on extra work and said I’d need time for the extra responsibilities until we decided on the increment. Then, the meeting happened with the co-founder and the manager, but they didn’t discuss the increment. They stated that I had stopped taking calls and refused to entertain this behavior, terminating me immediately without notice.