SMS limit on iPhone

Your message may have been 400 characters long, but it was divided up into blocks of 140 and sent sequentially. In theory there shouldn't be a limit on the phone itself.

The messages have a 160 character limit. (140 bytes, but packed using 7 bits for western character sets).

In the UK on Vodafone the limit for a text message is 3x160 characters, in excess of that it is sent as a MMS message.

That also applies to inclusive minutes from your package, if the messages exceeds the 3x160 it is sent and charged as a MMS not as three text messages.

I think in the US Verizon lets you send up 7X160 characters to other Verizon phones, if it goes to another carrier it will divide them up. I guess it will very greatly by carrier.