Error in asterisk codec

After using a predictive dialer i noticed that the call is not going to the agent because of the error:

Sep 6 23:31:34 NOTICE[8187]: channel.c:1906 ast_read: Dropping incompatible voice frame on Local/913107773456@default-dd6f,1 of format g729 since our native format has changed to slin
Sep 6 23:31:34 NOTICE[8187]: channel.c:1906 ast_read: Dropping incompatible voice frame on Local/913107773456@default-dd6f,1 of format g729 since our native format has changed to slin


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