I worked at an NGO for 2 months, with 3 months being mentioned as probation in the Offer Letter. I am not a permanent employee. Offer Letter only mentions that I have to serve 1 month notice if i resign or pay 1 months salary in liue of. It does not mention their termination clause, or how much severance/notice they have to give if they terminate. Offer letter also mentions that they will cover all travel expenses, which they did not do in my last payment. Hence i resigned. But now they are enforcing notice period clause without paying my dues. I dont think i should serve notice period or trsvel any more because they might not pay any reimbursements again. What should i do?