Same old ISP NAT problem

Hi, I'm dealing with this problem for a long time now and i'm out of solutions.

I'm a simple man who wants to access from outside local network to my raspberry pi running transmission on a random port. The problem is always the same: my ISP NAT. I know that this is a well-know situation ad i've read a lot about it, unfortunatly without any result. Public IP and ISP port forwarding is not an option in my case.

On the internet seems that the only solutions are: 1. Reverse SSH: I did not try this in person but, from what i understand, it simply uses a VPS as an intermediary router to allow SSH connection from outside the network to my raspberry pi. The problem is that I want to access to a webpanel, hosted on http://localraspiIP:serviceport and, from what I can understand, this method can't allow me this 2: VPN: This is the choice i try initially, with strange result. My idea was simple. If I setup on a VPS an openVPN server, then i can connect bot my raspberry and my phone to this new network, obtaining "local" ip address. I manage to create this. My raspi was connected with a new interface tun 0 and a new ip address like 10.x.x.x . The same was my phone and all' seems correct. Ping from one device to another with the newer class A IP worked and the VPN was doing his job. But, even in this situation, trying to access to the transmission control panel from my phone using http://10.x.x.x: transmissionport lead me to another fail.

Now, with my bad English i'm asking if someone have suggestion. I really want this working all this problems are driving me Crazy.

Thanks to everyone who has the patience to read all' my post.