If you got a notice telling you that you have to pay those amount back, it should say why. You can also review the GST/HST credit eligibility here:: https://www.canada.ca/en/revenue-agency/services/child-family-benefits/gsthstc-eligibility.html The eligibility for the BC PST credit is here: https://www2.gov.bc.ca/gov/content/taxes/income-taxes/personal/credits/sales-tax

You can also contact the Canada Revenue Agency (CRA) directly & discuss it with them. 

If you are in Canada or the United States, you can call the CRA at 1-800-959-8281. If you are elsewhere, you can call 613-940-8495. This page has more ways to contact the CRA: Contact the Canada Revenue Agency

Again, you would need to contact the CRA if you are not sure why they are making you pay back these amounts.