Stock transfer within company code

Hi,

Within compnay code 0020 we have multiple plant &  each plant is having different business unit

For example plant 0001 is selling car & spare parts also.  Another plant 0002 provide service only.

As both the plants are under same company code when we are doing stock transfer from 0001 to 0002.

0001 is expecting payment from 0002 against the material supplied. As per my understanding as we are doing STO within co code we cannot do miro or anything for STO.

How can I handle this situation as they are diffferent business unit plant 0001 expect payment from plant 0002

Thanks,

Kiran