You typically don't spell out shorthand or acronyms for units of measurement, especially if the shorthand is not easily pronounceable.
In this case, say "gigabytes".
Colloquially, native speakers may also say "gigs".
ell.stackexchange.com/users/44151/Curtis White
With units of measurement like that, you write them without any plural marker, but say them with the plural marker Examples: 64GB → Sixty-four gigabytes 1GB → One gigabyte 30km → Thirty kilometers 1L → One liter 2L → Two liters
As for saying 'Gee Bee' instead of gigabytes, that's harder to answer, and probably up to personal preference to a certain degree.
It sounds a little bit like something my technically illiterate parents would say
My phone has 64 gee bee
But as a counter example, I often hear things like
My internet is slow, I'm only getting 300 kbps (said kay bee pee ess , stands for kilobits per second )
I also agree with people saying
My phone has 64 gigs or I have a 64 gig phone
Those are probably the most natural and casual for GB specifically.
ell.stackexchange.com/users/48073/Joe Pinsonault
The answer may vary regionally.
I would pronounce a "64GB phone" as a 64-gigabyte phone (Notice that there is no -s on gigabytes here because "gigabyte" precedes and is modifying "phone.")
I would not call it a 64-gig phone or a 64-gigabyte s phone, although I would understand what someone meant if they used either of those expressions.
I have a 64-gigabyte phone.
If the question were about "64GB of RAM" in a computer, I would pronounce it as either 64 gigabytes of RAM --or-- 64 gigs of RAM I am thinking about buying a computer that has 64 gigs of RAM.
I am thinking about buying a computer that has 64 gigabytes of RAM.
ell.stackexchange.com/users/None/
The most common would be to say it fully.
A phone with 64 gigabytes.
Note the plural 'gigabytes'.
It's also fairly common to say A phone with 64 gigs.
Though this is more informal, it's usually clear in context what the unit is with only the prefix.
This is similar to how someone might say That stone weighs 100 kilos.
ell.stackexchange.com/users/30474/Tofystedeth
Should I say "A phone with 64 gigabyte." or "A phone with 64 GB (simply pronounce the letter 'G' and 'B').
" To answer your direct question, I would say: I would like a phone with 64 gigabytes of RAM, please.
(You have to put in the units, otherwise it is like saying "I want a phone with 42").
To say "GB" sounds like "jeebee" as in Heebie-jeebies .
I think you would get a blank look if you asked for "64 jeebee".
More colloquially you might say: What have you got with 64 gigabytes?
They will probably realise you mean RAM and not buttons or cameras or something like that.
ell.stackexchange.com/users/21223/Nick Gammon
If I want to buy a phone with 64 GB, how should I say it?  Should I say    "A phone with 64 gigabyte."   or    "A phone with 64 GB (simply pronounce the letter 'G' and 'B')."   which one is more native?
How to pronounce 'GB'?
ell.stackexchange.com
<pronunciation><reading-aloud><abbreviations>
ell.stackexchange.com/questions/117075
ell.stackexchange.com/users/42104/柴玮杰
The most common would be to say it fully and in this case, say "gigabytes". "Gigs" is also a commonly used contraction. You might be misunderstood if you say "jeebee". Depending on the region, the answer may vary. Most often, native speakers say the full word, "gigabytes", in plural, perhaps making the addition of "gigabytes of RAM". Native speakers often say "gigs" as well. Another option is to say it as "a 64-gigabyte" phone. Saying "GeeBee" would probably not be understood or would sound odd.
Most often, native speakers say the full word, "gigabytes", in plural, perhaps making the addition of "gigabytes of RAM" Saying "GeeBee" would probably not be understood or would sound odd. Native speakers often say "gigs" as well. Another option is to say it as "a 64-gigabyte" phone. Depending on the region, the answer may vary.