800-774-3379

This is a customer service number for DSL Extreme, ISP. Not a spam caller.

It's DSL Extreme customer service.  In my case, they were calling to address an issue I had emailed them about (tech support).  Not spam or sale.

"We are sorry. The App has failed. Good bye."
First time I've got a call like that. I figured they were trolling for Phone numbers people actually answered.  But the other posters here say it is DSL Extreme and I am currently a new customer with them.

While the number IS DSL Extreme, that does not mean the number couldn't have been spoofed by a scammer

This number is also used by phonepower as an outgoing phone number. I suspect that either DSL extreme and Phonepower are the same company, or they share the same callcenter.

As always never provide any personal information to any caller as caller ID may be spoofed.
Call them back, if you have service with either Phonepower or DSL Extreme and ask them to check the reason why you have been called.