I can't test this on my phone, since it doesn't give me the option to save contacts to SIM, but I believe there's a hard limit on the length of contact names. If you want to avoid this limitation, you'll need to save contacts to a cloud account (it's easy on Android - just sync to your Google account) or directly to the phone (less preferable, because you'll lose all your contacts if you ever lose your phone or have to swap it with another).