How to proceed? I am confused.

I am working in an XYZ company, but I am working in a client location zxy company. For the past 2 years I didn't get any hike, so zxy company told me we will change the vendor. But when I am about to resign from XYZ the zxy company HR is saying don't we will recheck with XYZ company. But in the past 2 years XYZ company has promised multiple times like More then 30 times this month your hike will be given but never happened still now.

What I should do now ?