Cell C Reduced benefits without disclosure

I bought a giga 100 simcard recently as my last one was used up. I tried too roam on vodacoms network with it an was unable too and after a long week of trying too get some service from Cell C, i was told that the giga 100 now has been changed and you can roam on vodacoms network, even though the previous one did. If that was the case, i would never have bought it! My handset sim can roam on vodacom and prepaid sims can roam on vodacom, just the giga100 which they conveniently changed .This has infuriated me as this card is useless too me now so i will no longer do business will Cell C. My mobile handset contract expires this month too so im not renewing it!