Thoughts on a offer letter without any signature of the approver and no CTC breakup?

I received offer letter from a company which was not even giving me offer letter before but just a offer mail that too just 1 day before DOJ. After calling them and demanding an offer letter, I received it and in the offer letter there is no CTC breakup amd no signature of the approver present but just the name. Has it ever happened with anyone? What will you do? HR kept gaslighting me and telling me that it's perfectly valid and legal which I know for a fact is not legal since there is no signature present.