Why won't my phone send text messages?

[AC Question]

Hi everyone!

Just got a new Lenovo A7000 running Android 5.0 and apparently it just won't send any text messages. I can receive them normally, but as soon as I try and send it gives me a "Message not sent" and posts the text with an orange warning sign. I've tried installing another texting app but it still won't send anything. I also don't think it's a carrier issue, as the phone is dual-sim, and both sim cards get the same error when I try to send. Any help?

 

[Rukbat]

If the text is longer than 160 characters (80 if the language you use needs Unicode characters - accents and that sort of thing), it goes via MMS or it's broken into 160 character messages. Make sure that either your APN is set correctly for your carrier (with 2 SIMs, you'll need 2 APNs) or that your text app is set to break long messages (or not send them as MMS - it means the same thing).