Angered by South Africa's refusal to relinquish control of Namibia, the U.N. General Assembly yesterday unanimously called for the Security Council to impose mandatory sanctions to try to end Pretoria's defiance.

The assembly, winding up a week-long debate that began with a South African attempt to take its seat in the chamber from which it has been banished since 1974, adopted 10 resolutions strongly condemning South Africa's policies in Namibia.

The United States, Great Britain, Canada, France and West Germany -- which devised the U.N. independence plan and denounced the sanctions call as "inappropriate" -- abstained in all 10 votes.

South Africa has governed Namibia, the former German colony of South-West Africa, under a mandate granted by the League of Nations and has defied U.N. calls for the territory's independence.

In Bonn, West Germany rejected South African allegatiaons that the U.N. General Assembly president, Ruediger von Wechmar of West Germany, consciously prevented South Africa from getting a hearing in debate on its expulsion from the assembly.

A Foreign Ministry spokesman said the envoy conducted his duties according to the statutes. Von Wechmar had accused South Africa of orchestrating the attempt to reclaim its assembly seat knowing it would be rejected. He said South Africa could use this to support its claim that the U.N. was biased and unable to supervise elections in Namibia.