I have built a trigger that is called when a contact/lead is updated. This trigger calls a @future method with a callout when a specific field (Email_Issue__c) starts off populated and is then saved to null.

One of our clients has a night batch upload that does an upsert on all its contacts and even though the Email_issue__c is not one of the fields being updated in the batch somehow the callout is going through. When looking through the bulk data load jobs we see the error CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY:itracmedia.InvalidEmailContactTrigger: System.LimitException: itracmedia:Too many future calls: 11:-- for about 100 of 5000 records it processes.

Can someone please explain why this might be happening and what i can do to fix this issue.

Trigger

trigger InvalidEmailContactTrigger on Contact (before update)
{
    private String emailissue {get; set;}
    if(Trigger.isBefore)
    {
        emailissue = null;
        for(Contact contact : trigger.old)
        { 
            emailissue = contact.itracmedia__Email_Issue__c;
        }
        
        for(Contact contact : trigger.new)
        {            
            if(contact.itracmedia__Email_Issue__c == null && emailissue != null)
            {  
                if(contact.lastName == 'ApexRunTestIssue'){
                    EmailIssueRemover.test();
                } else {      
                    EmailIssueRemover.removeEmailIssue(contact.id, emailissue, contact.itracmedia__session_id__c, contact.itracmedia__server_url__c);
                }
            } 
        }
    }
}

Apex Class:

public class EmailIssueRemover {

  // Static variable that assumes a test is not running
  public static boolean isApexTest = false;
    
  //Future annotation to mark the method as async.
  @Future(callout=true)
  public static void removeEmailIssue(String id, String issue, String sessionid, String serverurl) {

     String server = EncodingUtil.urlEncode(serverurl,'UTF-8');
     String session = EncodingUtil.urlEncode(sessionid,'UTF-8');
   
     Http h = new Http();
     HttpRequest req = buildWebServiceRequest(id, EncodingUtil.urlEncode(issue,'UTF-8'), session, server);
     if(!isApexTest){
       HttpResponse res = invokeWebService(h, req);   
     } 
  }
    
  public static HttpRequest buildWebServiceRequest(String id, String issue, String sessionid, String serverurl){

    //Build HTTP Request object
    HttpRequest req = new HttpRequest();
    req.setEndpoint('https://www.**.com/removeEmailIssue?sessionid=' + sessionid + '&serverurl='+ serverurl + '&type='+issue+'&id='+id);
    req.setMethod('GET');
    return req;
  }
  
  public static HttpResponse invokeWebService(Http h, HttpRequest req){
     HttpResponse res = h.send(req);
     return res;
  }
  
  // Wrapper method for "main" that we will call in the Test Class
  public static void test(){
    isApexTest = true;
    removeEmailIssue('test','test','test','test');
  }
}