Over 15 years ago I worked with a telco that had similar affiliate issues. We decided to stop paying any affiliate commission at all and evaluate sales after some time to decide to continue the experiment or not. There was a little decrease in traffic to the site but no measurable decrease in sales of new plans. There were several check moments and data validation after that, but sales numbers remained as they were.

The conclusion was that affiliate marketing claimed a lot of sales in their reporting, but the brand was strong enough (this company was #2 by market share in the country and #1 on most brand metrics) to get those customers without affiliate links.