I would like to start reselling VOIP services, pre-paid cards, callshops solutions, voip devices, a branded dialer is recommanded.
can you suggest a provider ?

which market do you want to focus on?

"I would like to start reselling VOIP services"
I hope you've taken a good look at the landscape of ISPs. I don't know what areas you are going to be interested in reselling in but for starting out in the VOIP resell business it's going to be difficult for you since at least here in the USA isps are favoring traffic only to select VOIP providers, usually the ones that sue them to get it.
If your just looking to startup shop reselling VOIP, make sure you have done your research since the problems you could encounter you won't be able to do anything about.
I currently use a VOIP service that's done through a company that doesn't resell but provides their own service and i've had all kinds of trouble because of my ISP. If this were just a reseller it would probably be even worse for them.

I see, and you are right, but i'm not in the united state, i'm looking for something like talkfree, but i need a strong VOIP provider with a lot of options.

What are the options you are looking for? and in which region....

callshops solutions, creating agent accounts, customizing rates, (branded dialer if possible)