Best SMS Text Messaging Provider

All,
I need your help and recommendations. I currently use Y*****t as my sms text messaging provider for a local restaurant but desperately need to find and move my list to another company asap. My account has been unusable for the past three weeks due to customer support's inability to fix my issue. Their lack of a telephone support option is a real killer to as their standard support has been taking 2+ days to respond to a message and on top of that they ask for information already provided which just delays the whole process.

My list size is about 800+ opt-in subscribers who I message once a week with a new deal for a restaurant. Price is always an issue but not the main issue. I want great and fast support in the event I need it.

Below are the qualifications of what I am looking for in an SMS text messaging service:

• fast & friendly customer service
• a support phone number where I can reach a human would be a HUGE plus
• ability for customers to join/remove themselves from list via a text message (ex, text Restaurant to 12345 to join our list)
• ability to send out about 4,000 messages a month (currently spend $149 month)
• import my current list of 800+ members (CSV format)
• sending messages to my list from cell phone would be nice as well (I previously had this option)

Please recommend any companies that you have had good experiences with. I so wish Aweber did sms text messaging!

Thanks for all your help in advance!