When I send a long text to a friend using stock app, she only gets the last part

Using Galaxy 5, stock Message app. Message I send is broken into blocks (that I don't see on my end) and only the last block is received on the other end, which is also a Galaxy 5. I get no error messages so the only way I know this happened is that my friend calls me because she doesn't understand the truncated message she got

Are you on verizon? If so, make sure that when you send the message it doesn't convert automatically to a multi media message (mms). That could be the problem ...

I'm on Sprint. How would I know if message turned to MMS?

Analog systems split the message at 160 characters check your phone settings for this feature

Sent from my HTC One_M8

I think it may be bc you're using the stock application....on verizon I'm using the Verizon messaging application and I don't have the texting issue you are speaking about...sorry, hope you find a solution