Email Marketing Software Support

We are looking for experienced freelancers in email marketing who can help with the client support of our email marketing software on a continuous basis. The support requests can be usually answered by email but sometimes it will also need a phone call. We are just starting out and don't have many clients at the moment but we will launch several marketing campaigns in the near future. So, this position would be ideal to do parallel to other freelance jobs in the beginning and will get busier in the future. Response needs to be as quickly as possible but should not take longer than 3 hours on business days. Most of our clients will be in the UK, USA and Canada. So we are looking for freelancers that can cover mainly the business hours of those time zones. We will pay by the hour and you will need to write a log book of how long it took to resolve a support request and invoice us accordingly. Please don't apply if you don't have much experience in using web based email marketing software. The budget I gave is just an estimate. You can go higher and lower.
Please state what experience you have in this area.
I am looking forward to your application.