You should raise your grievance promptly usually with your manager, clearly explaining the problem or concern and suggesting how it can be resolved at the informal stage, where appropriate.
Dylech godi eich achwyniad yn brydlon gyda’ch rheolwr fel arfer, gan esbonio’n glir beth yw’r broblem neu’r pryder ac awgrymu sut y gellid ei ddatrys ar y cam anffurfiol, pan fo hynny’n briodol.