Credit Limit Increase Issue

I have been trying to apply for a credit limit increase with no success. I have tried applying through the Whatsapp line, the ussd code line and online and I am getting no confirmation or feedback. When I phone the customer care I get put on hold and the calls just drop, or they just tell me to apply again. I have had my account for 3 years and this is the first time applying for a credit limit increase, but this process is proving to be a headache.