Hola Jose Manuel,
Thanks for your clarification, it sound really dark what I understand on my first read 
On a scenario like you comment:
..n't have contracted any support with SAP they cannot use the SAP support services for you....
For my understanding, any SAP customers, are forbid to contact SAP trough SAP support services, like oss message/incidents, mopz, etc...
Thinks on that 2 types of contracts:
1.- Direct Customers: They are able to Send OSS support message or request SAP service trough marketplace (that will change in the future), the best is to use their own SAP Solution Manager for that,
2.- Channel Customers: They are able also to Send OSS support message or request SAP service but they have to use "VAR" Solution Manager, because that VAR is the SAP partner that manage that type os customers license. That customers open solman tickects and if it is necesary Partnner have to send the incident to SAP.
3.- there are more type, like Large customers, etc.. but they use option 1 also, SAP partner is not responsible of SAP services.
I work at Seidor on the setup of VAR scenario with Solution Manager to allow all our channel customers to contact or request SAP services trough our SAP Solution Manager.
I think that this can answers you, anyone of that customers are on Risk to contact SAP Support, if you need more information you can contact me trough private message and we can talk trough mail.
Regards,
Luis