Dissapointing service from build it seshego

On the 20th of Feb I visited the build it in Seshego. I asked for a full quote for the installation of a fence. I was given a quote and told that I had received a huge discount. I was ecstatic. The total quote was R3590 after the discount and the manager put his signature next to the amount to finalise. I went home and made a few calls in order to organise the amount that was agreed upon as I am experiencing serious security problems at my place of residence. Today I went back to purchase and I was told that they made a mistake and that the amount would be almost double what I was initially quoted. The only explanation they can give me is that they made a mistake, but where does that leave me as a consumer, what are my rights? I've been a loyal customer of build it for years and I've never experienced anything like this, I'm extremely hurt and disappointed in the service I got from this branch.