Jas,
Generally companies (assuming it is an actual company as such and not for example, a firm or a partnership) cannot be sued for defamation. But there are some rarer actions a company as such could have for such statements.
Individuals can sue for defamation though. Of course, truth is a defence.
So it is in general ok to do so but I would be careful. You would be unlucky to get into trouble legally here. But there are other less legally risky avenues to express such grievances such as just not dealing with or recommending them to anyone.