Sim800L reveice sms mising characters

Hello i had a problem with receive SMS, it missing Characters that’s can only 13character.
i had change buffer RX in Software serial form 64 to 512 but still not working.
In image i send : H258x863x557x8278x908x890E
But receive only : H258x863x557x
Thanks in Advance

Faced this exact problem with Arduino Mega. Couldnt resolve it. The Arduino library uses some buffer settings, which are not easily found. Modified buffer size , but didnt work. Have to find the right file to modify the buffer sizes.