Existing Customer for 15 years - Mission for New Line

Good day,

I have been a Cellc customer for almost 15 years and I have never missed any payments. I am not the once to complain cos i have never had any issues. I am currently on a month to month and have been due for an upgrade since 2019, agents called me on several occasions to upgrade but was not happy with the specials offered. My issue is that i have a credit limit of R**** to process an upgrade yet I do not qualify for a new line that cost R169. Please can you explain to me why? The agents are so quick to call for a SALE but forgets to provide feedback. I have logged many cases with Customer Service but as usual no feedback.