There are three ways to pay for a subscription: SBP through YooKassa, Telegram Stars and your internal account balance. You choose on the payment page, which also shows the amount for each option.
The main route for paying in roubles. After pressing the payment button you move to your bank's app and confirm the transfer with a QR code or a link.
Payment inside Telegram with Stars. The invoice arrives as a message in the chat with the @obfsnbot bot, and you confirm it there. It suits you when SBP is unavailable, for instance if you have no Russian bank. The amount in Stars is shown on the term cards once this method is selected.
These are bonus roubles credited for completing tasks. Balance can pay for a subscription in full, like ordinary money.
First check whether an invoice is still open: on the payment page a started payment continues where it was rather than creating a second invoice. If your bank declined the transfer, try another bank in the SBP list or pay with Stars. Promo codes and bonus days are not payment methods: they add days to the subscription directly.