The Washington International Studies Council operates as the Oxford Study Abroad Programme, which is a division of WISC. WISC is the legal company name, though operationally WISC and OSAP are the same program (same staff, same services, etc.).
In short, OSAP is the trading name of WISC.
All institutions and students who had been previously applying using a WISC application, or via the WISC website, should now use the OSAP website, linked below.
Should you have any questions about WISC or OSAP, please visit the OSAP site linked above.
The Washington International Studies Council (WISC) is accredited by both the Quality Assurance Agency for Higher Education (QAA) and the British Accreditation Council (BAC), and holds a Tier 4 Sponsor Licence from U.K. Visas and Immigration. Details for all of these can be found here.