Makro does not get bakc to a person

I have emailed and tried to contact Makro regarding a credit note issue and I have not had any success. On a previous occasion when I returned goods to Makro, Makro issued me with a gift voucher card. With the last return (which I returned because it was not working), Makro refused to give me a gift voucher card, but instead issued me with a credit note. My issue with the credit note is that it is only valid for 6 months, whereas a gift voucher is valid for 36 months. I recently now discovered this credit note of mine has just just expired, and I want to confirm if I can still use it... but no one at Makro is interested in getting back to me.