You are micromanaged to hit unrealistic metrics. Your pay and shift options are based on a bell curve which inherently means 15% of employees MUST fail to meet targets... it's a quite insidious way to push performance without parallel employee compensation.
Monolithic corporation downside is you will simply be a number which generates numbers.
Pay stagnates with tenure. Some instability with centers closing, layoffs, and more reliance on cheaper (and worse) independently contracted call centers.
The job can cause very high stress and anxiety levels. Pretty significant attrition.