You can buy a line for a client from your personal account, without going to partner's or client's account. do this:
1. Go to your personal ChatApp account;
2. In the Left Menu, select "My Business";
3. Click on "Buy a Line";
4. Click on the "Buy for a client" slider;
5. Select the client;
6. Select the subscription period;
7. Select the desired communication channels;
You can bill the client's company. Read more in the article - "How to invoice a client".
8. Click “To Pay”

9. Select a payment method:
INVOICE - payment by requisites;
RoboKassa- payment by card;
Bonuses - payment by bonuses;
From your company wallet
Read more about payment methods in the article "Partner Cabinet payment methods".