i have the same problem ... Help !! Why are they not showing up on line Billing and on statement?

I receive text messages that are not showing up on my ATT wireless bill. Does anyone know if this is common? I know I received the texts, but the bill which normally shows the telephone number from which the text was sent doesn't reflect the text was received. For example, I received a text on my phone from 555.555.5555 and this number would normally show up as an incoming text on my bill. However, it seems like in certain circumstances there is no record of the incoming text. Am I losing my mind????