I left the company and I have to repay the relocation expense paid by them.
1) Company has hired some moving company and in the moving expense they have included the amount paid to that moving company.
Will I have to pay back the amount paid to moving company for their services, which the company had hired for their convenience?
2) Company has included some Tax assistance on the moving expense. Will this Tax assistance amount I will get back while filing the return? When I am paying the whole expenses paid then why I need to pay any taxes?

Please advise.

What does your employment agreement state about these expenses? The agreement is a contract and BOTH parties are bound by the terms.

Why would you not expect to have to pay the company back for the money it spent to relocate you when, for whatever reason, you have left the job?

I don't understand your reasoning - the company hired a moving company to move YOUR things to the new location for THEIR convenience? How did you intend to move your belongings and why did you agree? Nobody is coming into my house and moving my belongings without my consent!

If the company paid you an amount to offset additional taxes, yes, that is income to you. Of course, your moving expenses are now a deduction for you if you meet IRS guidelines.

Unfortunately when you sign on to a new company that reimburses you for moving costs and they "true up" the amount to cover your income taxes on it, and then you leave before the agreed time limit, it's a mess. Yes, you probably have to pay the full amount back - the amount of the reimbursement plus the tax true-up. As JudyKayTee says, rad the agreement tat you signed to verify this, and see whether you can deduct the moving expenses paid to the moving company. Unfortunately even if you can deduct these expenses it won't quite make you "whole" - you are out the cost of the moving expenses plus income tax on the true-up amount.