ESD clamping voltage in SIMCard interface too high
ESD diodes will dramatically reduce the effect of ESD pulses. You are right that the clamping voltage is still pretty high, but that is under specific test conditions that may not apply to your design.
What you should do is put in the ESD diodes, as recommended. For any data lines, you can add some series resistance (start with 0 Ohms) and maybe a capacitor, too right at the input to your IC, and then build and test.
If you pass ESD testing with no capacitor and a zero ohm resistors, great. But if you don't pass, then you have the option to put in the additional filter elements, and hopefully signal integrity will still be OK.
For the RF input and output signals, do not improvise. Do it EXACTLY the way the manufacturer recommends. No extra components, and no substitutions. The reason for this is that RF inputs are very sensitive to any change in impedance. You have to implement that part of the circuit as recommended, or you risk seriously degrading the performance of the GNSS system.