Selecting one random data from a column from multiple rows in oracle

I am creating a view that needs to select only one random row for each customer. Something like:

select c.name, p.number
from customers c, phone_numbers p
where p.customer_id = c.id

If this query returns:

• Customer1 1
• Customer1 2
• Customer1 3
• Customer2 4
• Customer2 5
• Customer3 6

I need it to be something like:

• Customer1 1
• Customer2 4
• Customer3 6

Rownum wont work because it will select only the first from all 6 records, and i need the first from each customer. I need solution that won't affect performance much, because the query that selects the data is pretty complex, this is just an example to explain what I need. Thanks in advance.