Effect u/s 90 to 91A

Good morning,
Need your advise,

On our Global Income ,clients withhold a tax amount and issue certificate of deduction.

Can we, as an Indian Company claim back the WHT amount in our annual tax return or should we go by u/s 90 to 91 of IT Act and avail only 2.5% On the Turnover Only.

If we obtain a Tax Residential Certificate for our Company from the Concerned Jurisdiction officer and submit it to overseas clients for non deduction of withholding tax.is it acceptable