problem with Samsung E900

Hi, I topped up my phone with $ 27 on the 5th of December with my debit card, this was for 675 texts only. I have been trying to send texts for 3 days now and everytime I try to send one it comes up incorrect number. My friend said, this happens to her when she has no credit left. At the best of times I don't use my phone much but I was in hospital 2 weeks , so hardly sent any texts. My phone log shows I sent 31 texts over a 2 week period which is about normal for me but there is no way I have sent 675 text in this short period of time. What could be the problem and what action can I take?
Thanks.

which service you are using?

Oops sorry . I'm using Vodafone.

The problem you are having doesn't necessarily mean that you are out of credit. Have you checked your balance? You can do this by calling 2345 or registering for a Vodafone online account.

If your phone is showing credit and you still can't send texts then have a look at Vodafones Phone Troubleshooting pages for some checks that might fix it for you.

This should fix it for you