repo my deadline

Running a local newspaper which is available FREE to our community, we rely solely on our advertisers. Ruan Repo had committed to 3 months where they booked a significant size advert with us, and I have worked with them before, and I did not battle to get the payment from them. This time round, I have been sent messages day to day making different commitments that were never upheld. I have now been blocked, and I have commitments that need to be maintained, and because of non payments, I have been put in a terribly uncomfortable situation and also have been put in a predicament with deadline which implicates the rest of my paying clients. This is so incredibly unfair. If this is what they do with their advertisers, how do they treat their clients?