Legally you must get your holiday time, but there's nothing about whether it's acceptable to make contact or not, that would normally be for negotiation between employer and employee as to whether the employee is happy to be contacted and about what type of issue.
If you spend a chunk of time dealing with issues when you are supposed to be on holiday I would recommend asking for a day or half a day holiday back.
If what they have contacted you about really wasn't necessary, let them know that you weren't happy about it but felt obliged because of the 'ASAP', and would prefer not to be contacted again.
As mishymoo said, you could have been abroad or not contactable. I am assuming they knew you would be around though?