Why are the shipping labels for these Plug-ins (USPS/UPS) not being paid from my accounts

Customer :

Why are the shipping labels for these Plug-ins (USPS/UPS) not being paid from my accounts. We are processing labels in the back end of websites? Please advise how to accomplish this?

Support :

For UPS, postage should be automatically deducted on creation of label in live mode.

For USPS, the plugin does not have automatic postage payment mechanism as USPS API does not have an option for that.
However, we do have a Stamps plugin using which you can pay for postage online. In that case, you would need a Stamps account.