Caltex Woolworths Gift Cards - Can I Use at Woolworths?

I bought the Caltex Woolworths gift card from Groupon last week. Wondering does anyone know if it's redeemable in Woolworths as well or just at Caltex? At the front of the card. it has both the Caltex and Woolworths logo so it makes me believe you can redeem at both.

Tried looking online and checked their website and no answer.

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