Customer is saying they are dropping 2-3 calls a day, doesn't matter if it is incoming or outgoing.

Aside from swapping the card in the 8100, is there any way to determine if it is the system or Telco issue? When the issue occurs, it then takes 10-15 minutes to restore before calls can be made or received again.

I have used DIM before for other issues but not sure if it will show how or why the PRI is dropping.

99% sure it will be a carrier issue. These systems are like tanks. I mean you could switch out the PRI card but it would like not work at all I would think. If a plain Jane PRI look at the CSU and the UPS. If an IAD same and check clocking. The 10-15 minute thing seems fishy to me and if it's an IAD it should be generating errors.