Import Activites and associating with Account, Opportunity(Deal) etc.

Import Activites and associating with Account, Opportunity(Deal) etc.

I've tried to import an activities csv file several times today. The file will upload and all field mapping works except the account will not match up to the related to field.

I need a way to mass upload activities and have them match up to the account, deal, contact they were created for.

Any suggestions?