text massaging issue using at&t not getting msgs right?

[gina]

hello and sorry for bothering people. i have a samsung galaxy s3. model number samsung-sgh-I747. my issue is im not getting long text messaged right. first i didnt get the whole thing just the middle of it. now im getting the whole messaged but out of order in single lines.i looked at tons of videos and i downloaded new text messaging apps to see if this issue would change like go sms pro. nothing. its really annoying. i looked at youtube videos to. some one said to go into text settings and change the input to gsm alphabet. so i did. was working for awhile. before that i called at&t and they said the sim card signal was a little weak. so i got a new sime card. the person im texting has the same phone but for verizon. it was fine between us at the start. its been messed up for three weeks now. he called about his phone aswell. they told him nothing was wrong on his end that its me. and on my end they said it was him. im ready to throw this phone against the wall. i send text messages to other att people fine. this is driving me nuts. please tell me what i can do. i took out the battery and the sim card put them back in. turned my phone off and on. cleared data. deleted old messages.cleared ram. force stop on any programs i dont even use. turned mobile data off and back on. i dunno what to do anymore.