VODACOM DOES NOT HONOUR THEIR CONTRACTS !!!

We are a business that deals with many small vendors, we developed and app that will help our vendors in sales and marketing our products. Vodacom approached us to supply the hand sets and we agreed, documents were signed and approval was given after vetting our company to see that we qualify. After that we were told that there is a shortage of stock and we should wait an extra week by Vodacom. We agreed and told our vendors that we will be getting the phones next week. 1 Week passed and now we are told that we should pay upfront for the 24 months contracts after being approved!! In which sentence does it make sense to sign a 24 month contract but pay upfront after being approved for the contract ?? Does Vodacom know what it is doing or are they just blatantly stupid, why approve us and then come up with a silly excuse, why put the vendors who are small business and supporting their families through this aggrevation if you have no intention of honouring your word!! Is Big Business in South Africa allowed to get away with this, should they not honour their contract!!!

If VODACOM is allowed to not honour their contracts with clients then why should clients be forced to honour their contracts with VODACOM???