Cannot contact certain numbers with minutes?

I did not know that cell c doesn’t allow you to contact certain numbers with the minutes you purchase. 087 and 086 numbers can only be contacted if you purchase airtime separate to your contract minutes. I have never experienced this before with other networks and is certainly a nuisance. I should be able to contact who I need to because I purchase minutes monthly via my contract. Very distasteful way to try make an extra buck. Only problem is a family member of mine also has a cell c contract and has no trouble contacting 087 and 086 numbers? Without purchasing airtime...