Insert data in two columns same table

I'm trying to insert data from TABLE A to TABLE B.

1 - Select billable_id from dm.billable
2 - Select mobiuser_id from ja_mobiusers
3 - Insert the billable_id and the mobiuser_id to the dm.billables_links
table.

*FYI -* It has to be in the same transaction because the mobiuser_id must
go to the selected billable_id on the first select.

Well... Would be something like:

> INSERT INTO dm.billables_links (billable_id) VALUES ((SELECT billable_id
> FROM junk.wm_260_billables2 WHERE info ilike '%Alisha%')),
> INSERT INTO dm.billables_links (mobiuser_id) VALUES ((SELECT id FROM
> public.ja_mobiusers WHERE name_first LIKE 'Alisha%' AND name_last LIKE
> 'Dson%'))

The problem is that I need to do that at the same time, because of a
constraint:

ALTER TABLE dm.billables_links
ADD CONSTRAINT cc_one_and_only_one_target CHECK ((("customer_id" IS
NOT NULL)::integer + ("role_id" IS NOT NULL)::integer + ("mobiuser_id"
IS NOT NULL)::integer) = 1);

I'm having trouble by creating that SQL... can anyone help please?