German pension

I receive a German pension from Berlin.

I have not been paid for the last two months.

The reason is (I think)  because I did a bank switch,

I have tried to get in touch with Deutsche Renten Versicherung but I can't call. No one answers.

Any ideas how to get in touch with them?

Thanks

Send them a registered letter - only that is accepted as legally valid communication (and not phone calls). And don't expect German officialdom to reply or do their work quickly!

will do. thanks