unused minutes roll over

Some providers allow unused minutes /data to roll over to next billing period. 
Please consider this. 

What steps will reproduce the problem?
1.
2.
3.

What is the expected output? What do you see instead?

What version of the product are you using?
"Last" is not appropriate. Make
sure you tell at least which app you are using. On what operating system?

Please provide any additional information below.

Original issue reported on code.google.com by alistair...@gmail.com on 18 Jun 2014 at 10:31

Merged into: #100

waasilzamri / callmeter

unused minutes roll over #988