with my old dumb phone I did not have a data plan but I could send and receive text messages anyway. Now with my samsung s5, if I turn off mobile data and connect to wifi I cannot send a text message.
SMS/MMS messages do not count against your data allowance. MMS messages are sent via cellular data, however will not count against your data allowance. SMS messages should be able to be sent with cellular data turned off.
Well it doesn't work that way on my s5. With mobile data turned off I
cannot send a text message.