If your payment has just been rejected, that could mean that your account will go back to a free member state very soon.
However, please note that in a free user state, no data is lost, and all your opensolr indexes remain intact.
However you might experience a certain downtime, due to the low limits of a free account, especially if your free trial has ended.
In order to avoid any downtime, the best option is to simply place a new order, at https://opensolr.com/pricing
When placing a new order, you can use a new payment method, and the old order will be canceled and will no longer bill.
In case your previous, old order is still in effect and active, you will also receive a refund, for the remaining unused days of your previous membership.
All the above is being processed instantly.
Alternatively you might want to opt-in for yearly checkout, which also enables a certain discount for your purchase.