New phone, old SIM - any benefit to switching to new SIM?

[JoeyJoeJoeShab]

Some history:

1. was on a 4G plan (old phone, old SIM) for years 
2. recently changed to a 5G plan, unsuccessfully tried the new "5G" SIM (phone couldn't make calls or access data) - i figured my old phone didn’t support 5G and/or Public didn’t support it and 5G so i just put the old SIM back & changed back to my 4G plan 
3. some time later, my old phone just stopped being able to make calls or connect data 
4. after some attempts at getting it to start working again, I retired it & got a Pixel 8a

So, now I have a new phone using my old SIM (I still have the new "5G" SIM here).

But I see that my new phone is on the 5G network, so I'm not sure what the deal is.  Is it that it's *on* the 5G network, but not actually taking advantage of the speed of the 5G network?  Are there other benefits I'm missing out on?  Is it a no-brainer for me to just flip over to the new SIM? 

[BKNS27]

@JoeyJoeJoeShab 

Guess you got a free SIM with your subscription.

You can give it to a family member or friend but have them use your referral code.

[JoeyJoeJoeShab]

Thanks for the responses, much appreciated.  Guess I'm wondering a little bit why they sent me a new SIM, but I assume they just do that (?).

[BKNS27]

@JoeyJoeJoeShab 

The PM SIM will work on 3G to 5G so the old SIM will connect to the the plan you are on. Therefore, you will be 5G if you are on a 5G Plan as long as the setting in your phone is compatible to 5G and set to 5G.

[RAZOR_MARK]

no need to change to new sim card, because there is no difference at all

[Rastin]

The sim doesn't make any difference on weather you get 4g or 5g. Your 4g plan just limits your speed but you can still connect to a 5g signal. And the speed difference is not noticeable for the majority of people anyway

[fixin1 · Accepted solution]

@JoeyJoeJoeShab - Any Public Mobile SIM card from 9 years onward does not need any new card for 4G nor 5G, just the phones software needs to support 5G and the carrier profile.

LTE and 5G are very similar here, maybe a little faster on 5G but not noticeable.