Telkom night owl special expired

Telkom had a special where you could buy night owl data 500gig for R50. This special was discontinued, but when I bought it before it was discontinued in April, the internet site stated that the gigs I bought will not expire but that I can use it until its finished. I bought 2, therefore a terabyte. But on 18 May it expired and without knowing I used up all my day time data. I contacted Telkom to resolve this but they just say it shows no data everything has expired. I don't know what else to do.