An hour has 60 minutes.
If each call lasts an hour, the total amount of money charged is 60*.05 = $<<60*.05=3>>3 for 1 customer.
When she talks to 50 clients in a week, the total amount of money charged is 50*3 = $<<50*3=150>>150.
In a month of 4 weeks, the phone bill is 150*4 = $<<150*4=600>>600.
#### 600