The setting is on Earth in a not distant future (imagine 150/200 years).
AIs manage most aspects of society, including justice administration. They are extremely efficient and can quickly solve complex problems but they are not sentients. Imagine a litigation being solved in minutes instead of years like we do.
Humans with Brain Computer Interfaces (BCI) are linked with AIs and provide generic guidance and overseeing. Basically humans with BCI are the reason why AIs are not sentient. BCI humans are the sentient part of the AI.
Society has moved to cashless for all official transactions since a long time. All (official) transactions are monitored by AIs.
A vast underclass of citizens don't have access to BCI and are therefore relegated to minor, low paid jobs and limited access to basic services. To survive they are usually organized as "clientes" (AKA clients) of a "patronus" (AKA patron).
These terms are a vague reference to the relationship that was formed in ancient Rome (see Patronage in ancient Rome) in an attempted embellishment by those who profit from it. But the actual nature of the connection in this question is fundamentally different.
First of all this kind of relation, although widely known, has no official digital registration and is not managed nor monitored by AIs. It has therefore no legal bonding. It is merely an utilitarian bond between the two parties in which both gain although not in an equal, balanced way.
Breaching the relation would cause a severe loss of trust though. For the client it would be impossible to find another patron, for the patron it may be difficult to acquire higher standing clients with only the more desperate ones (and thus those with less skills) seeking him out.
A smaller part of this underclass, the one most in need or with the lower skills, has to give themselves into service to organized syndicates that operate outside of the law.
It does exist a parallel 'deep web like' network where profiles and positions are stored and shared. Since all payments are monitored by AIs because of the cashless society patrons can't pay someone officially to rig an election or to incite a riot or other shady activity. Paying people officially for an item or service but then obtaining a different service (e.g. a riot) would be hard to arrange and would lead to too many traces in the system. For instance an AIs would quickly find out that many of the identified rioters had recently business transactions of some kind with a specific patron. This would lead to very embarassing questions, especially if the same pattern emerges multiple times. While the higher level patrons may be anyway above the inspection of the law lower tiers need to keep plausible deniability.
The use of clientes by patrons covers activities that are illegal or would bee too expensive if done in full compliance with the law. For instance:
- voting in local elections. A patron with a large base of clients has considerable local power. Some patrons may make arrangements with higher tier patrons to pursue broader influence.
- menial activities that are ill suited for robots without paying due taxes, insuarance, retirement.
- sexual exploitation
- organized rioting
In return clientes are given items and access to services they would not otherwise afford : food, medicines, clothing, access to virtual reality with its plethora of services.
Of course different clients are suited for different tasks. This is where organized syndicates step in by facilitating the exchange of clients among patrons as well as using them for their own needs.
While it may be difficult for a patron to exchange his client who is a beefy 40 years old male weighting 100 kg to another patron who is looking for a petite young female the Syndicate may arrange the deal being able to pick from a very large pool of patrons and customers.
Clientes may be exchanged also against items, services, political support and so on. This items would be bought legally by the patron or Syndicate.
Provided that the authorities keep looking the other way (as many of the elite members are also benefitting from this system) and will not take action against it would this system of 'currency' work?
Note that clientes are NOT slaves. In order to induce them to perform a certain task they need to receive an adequate benefit in return. While abruply leaving may hurt their future living conditions, it is certainly in their possibility to do so. Of course, if this caused damage to a patron or Syndicate they may have someone after them who would like to have a friendly explanation on how breaking bonds may lead to some other kinds of breaking...
Note to edit: edited to improve the explanation of the client / patron relation. Improved explanation of the need to avoid official payments. Improved some examples for further clarification. Added detail explaining non sentient AIs