Rejection of existing customer contract - Auto lim

Been on a Telkom contract of R400 pm for a year. When trying to take out another of R100 pm, got rejected with no bad credit record, no skipped payments. Lady said I should phone HO to ask why, did also not want to tell me why. Ensisted on m y spend limit being reduced to 0, and taking out a contract somewhere else, now they keep on increasing my spend limit on existing number