The usual "unusual high call volumes"

I've had issues with a number of deliveries over the past year where drivers could not find the delivery address or were they send out a delivery notification only to delver a day or two later. And on every occasion they were "experiencing unusually high call volumes" which resulted in me having to wait 5 minutes or more for someone to attend to my call. And in the event of losing a call you have to start the process from scratch. If your constantly experiencing "experiencing unusually high call volumes" is is still unusual? I'm no expert but perhaps you should get more agents to attend to the calls. Trying to escalate the matter also resulted in nothing so I guess the managers were experiencing unusually high workload?