You can view all the payments you have made to CallHub under Payment history in your dashboard. You may check this under credits option after clicking the $ sign and then click on View under the Payment history section.
If you wish to download the receipt, you may follow the instructions given below.
You need to print the page to download it as PDF, you need to use Ctrl+P(for windows) and command+P(for MAC). A pop-up will appear where you need to choose "Save as PDF" from the dropdown and click Save to download the receipt.