I find this, of all the toxic DXC behaviors, one of the more toxic behaviors.
So in order to get a pay rise, you need to find another company willing to hire you and go through the entire interview process (which could be four or five interviews) to get that signed letter of offer.
You take that letter of offer to your manager and DXC will match the toppling salary. They will never match the bottom line take-home salary.
What a titanic waste of time for the employee and the employees of the company that you just interviewed at. The level of disrespect here for everyone involved is immense.