If cellnuvo has technical difficulty in making payments to redpocket for members, it can offer its business credit card to redpocket so that redpocket can set up an alternative payment method for cellnuvo members. When a cellnuvo member refills, he just chooses cellnuvo credit card in his redpocket account to checkout. The credit card numbers can be hidden, and the payment amount can be limited. This would solve all problems.
I would imagine that this is essentially the way it's already done, except that I'd be surprised if CN is processing payments one at a time to Red Pocket, under the system we've been dealing with.
I would guess that CN would pay in bulk, either by depositing a chunk of funds in advance, or by invoice. Dealing with payments $5 at a time is not efficient, either for CellNuvo or for RedPocket.
With the new process, your scenario is probably closer to the way it will have to work with multiple providers. Maybe a system as I've suggested above for 'preferred providers' (perhaps Red Pocket and Amazon?), and a direct per-request payment method like you suggest everywhere else. The processing costs are higher in this scenario, either for the payer or the payee, or both. (Of course, the payee likely already has those single-payment processing costs figured into their rate structure.)