increasing my limit without my permission

i called homechoice several times asking them not to increase my limit the agent who assist me said she will put a note ,within 3 months the increase again, I called service desk and zandile s team leader referred me to Transunion as she claims the don't have any control for my limit to be increase and she stated that she cant reduce the limit either, this is affecting my scoring and affordability I want my limit to be reduced