If you believe that you should demonstrate the strength of your apparent no contact regime by allowing the narcissist to send you text messages so you can ignore them, you are being led by your emotional thinking and you do not have a no contact regime.
This is an executed, albeit unsuccessful hoover and you are placing your head in the lion’s mouth expecting it not to bite you. It will do so eventually. You do not need to take this risk.
You do not need to know what the narcissist is writing to you.
You risk becoming angered, upset, hurt, irritated or some other adverse feeling as a consequence of reading the text message.
Initially the narcissist will receive Thought Fuel if the narcissist knows the message has been received (although this is shortlived) and therefore this increases the risk of being hoovered (all else being equal in the Hoover Execution Criteria).
You are also increasing your emotional thinking by allowing this communication to take place, by reading it (or even if you do not read it) by being led to think about the narcissist (however momentarily) as this text message has reached you. This leads to the risk of reaching a tipping point which will cause you to respond in some way and thus you find yourself stuck on the Narcissist´s Wheel of Misery.
If you think it is entertaining to toy with the narcissist by allowing the text messages through and ignore them, you are being led by your emotional thinking which is corrupting your empathic trait of justice and/or narcissist trait of pride.
If you think you need to know that the narcissist is still interested in you (don’t worry, we remain interested until either you die or we die) you are being led by your emotional thinking which is corrupting your empathic trait of truth seeking and/or your narcissistic trait of pride.
Block the number.
Better still change your number.
Get Out. Stay out.