Trending @Infosys; Currently im serving notice period and infy is trying to retsin me

Cureebtly I'm serving notice period. Mylast date is june 5. Now suddenly senior manager comes into picture and says we can match the competitive salary and will be sending onsite opportunity.

How much we can trust these guys on on-site?? Will they send really? If i need these things in writing with whom.i should take it and who should be there in the email or acknowledged by?