Managing Multiple Advertisers? How Do You Keep Call Data Separate?

I’m curious how others are handling this when they have several advertisers running at once.

Once you have multiple advertisers and campaigns in the mix, keeping each call tied to the right advertiser and traffic source can become a bit of a headache.

Do you keep a separate tracking setup for each advertiser, or manage everything in one system and separate the data through campaigns or reporting?

I’m especially interested in how you keep attribution clean when you need to trace a call back to its original source.

What’s worked well for you, and what have you found doesn’t work as well?