Can't pass more than two arguments in an Apex Class Map - what can I use instead?

I guess you are fetching the Account from databases right - if that's the case, in your query try to fetch the Contact related details as well. After that, from Account - you can refer to a list as Account.Contacts. Size of Account.Contacts list could be >= 0 depending upon your Account and it's contacts counts.See below a sample code.

//This queries all Contacts related to the incoming Account records in a single SOQL query.
  //This is also an example of how to use child relationships in SOQL
  List<Account> accountsWithContacts = [select id, name, (select id, salutation, description, 
                                                                firstname, lastname, email from Contacts) 
                                                                from Account];
  // For loop to iterate through all the queried Account records 
  for(Account a: accountsWithContacts){
     // Use the child relationships dot syntax to access the related Contacts
     for(Contact c: a.Contacts){
   	  System.debug('Contact Id[' + c.Id + '], FirstName[' + c.firstname + '], LastName[' + c.lastname +']');
   	  c.Description=c.salutation + ' ' + c.firstName + ' ' + c.lastname; 
     }    	  
   }