If there is a trouble call, the call should go to you first, if you do not want to run the service call, then they will most likely charge you back, but you should be first option for the call since you did the install. And as far as your last check, just save copies of the orders you are owed for, and if they do not pay you, file a labor lein on the address you did the install on. If you let them know you are giong to do this, trust me they do not want the customer calling direct telling them their contractor is filing a lein on their property. You do the labor you are owed for it.
This is CABL.com posting #263554. Tiny Link: cabl.co/mbgI2