Assuming that you have set the data retention policy to 3 months or the default 6 month and you need to go back in time to a period before that, it is technically not possible for us to go back and restore this data as it has been completely removed from the Hard Drives, however we understand that this scenario might be frustrating so we have worked on this article to tell you some work arounds that should help you get the data you want back, i would be happy to tell you about this technique.
Work Around #1:
The industry standards for billing is 7/3, 7/7, 15/15, 30/30 you had billed your customers according to these standards a PDF or Excel invoice has been probably sent by your billing team every week, bi-week, month to your customers which usually contains the summary reports (Total Traffic Received per Destination) from the customer, you can use your e-mail history to download such data and find out the total traffic termination by each customer per month, week or bi-week.
Same goes for vendors, look out for incoming invoices from your suppliers for each month.
Work Around #2:
Most soft switches or voip billing software in the market today has a customer self-service portal, you can request CDRs web portal access from your vendors or customers and download the data you need from their billing system,
Work Around #3:
If your vendor or customer does not have a self-service portal of their billing system you may request CDRs from their support team for the period you need.
Work Around #4:
If you're using TelecomsXChange.com service to terminate your calls you can login to the portal and click on call stats, you can download old CDRs/Stats from the portal directly or you can look out for the daily TelecomsXChange CDRs e-mail which contains your daily CDRs backup on an excel/CSV format, if not then you must go with Work Around 1, 2 or 3.