DSR clearly presumes fixed connections.
This would seem to exclude cell phones, despite their rôle in DSR like ideas in Africa.
One of the Garage Door Crypto Schemes may save the day here.
When you are about to travel choose a big random counter value and put it in your computer or cell phone and also in some reliable well connected well known ‘Hserver’ that you trust.
Your arrangement with the Hserver includes it holding perhaps enough of your money to pay for DSR like payments while traveling.
You can transfer money the the Hserver while linked thru the static DSR network.
While on the road in range of a cell tower that does not know you, you initiate a call by sendingg the hash of the counter together with the ID of your favorite Hserver.
The local cell tower passes it onto the Hserver who has stored hash values of its clients counters, in a hash table (SIC).
This table identifies you and your account and thus your account with the Hserver.
The Hserver returns a message to the cell tower with sufficient funds for your purposes.
This needs study to understand vulnerabilities to cheating.