It is undisputed Irrefutable public knowledge NSA possess call records of EVERYONE who uses a phone in this country.
Since you specified domestic calls, to be clear those "records" are basically what is on your phone bill. Date/time, phone number, duration.
Nobody has any idea or can know what NSA does with it nor do they have any reason to trust the government.
Actually we know what they are doing. Building a connection network for a person(s) of interest. The FBI has publicly demonstrated such software, using only phone company records to develop such networks as part of organized crime organizations. They showed the topology of the discovered network and pointed out how it revealed middle men and meeting places that had previously been unknown.
The word "collect" does not mean "unless I use"
To be fair, they could simply order AT&T, etc to retain their records. Same data set. So without collection they could still get a warrant and explore the network of connections to the party of interest, as they had done with their (FBI not NSA) organized crime investigations. And what is the rejection rate of FISA warrant requests, 0.05% last I heard.
Now think back to that FBI work. How did they do their analysis? Most likely they had AT&T etc deliver complete data sets for various regions and they searched that data for connections. Basically, possession of the data does not require collection. One warrant can most likely cause bulk deliveries from telcos.