Sms Function modification/editing (C#)

I have my exe(c sharp)that I need an expert to modify the SMS sending function.
The SMS Function is implemented/encoded using the GSM-7 character set.
The 160-character limit is for messages.
When sending a Message, the receive receives the messages in multiple segments of the message.
The messages reach the target phone/receiver as multiple messages.
Now I want an individual who can implement Message Concatenation(For long messages) so that messages are linked together.
To arrive in the recipients’ mobile phones as one long text message rather than a string of individual texts(Segments).
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