HackTheBox - Challenge - Crypto - Bank Heist Writeup
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So this one was mainly easy. When glancing at the garbled text:

444333 99966688 277733 7773323444664 84433 22244474433777, 99966688 277733 666552999. 99966688777 777744277733 666333 84433 443344477778 4447777 44466 99966688777 4466688777733. 84433 5533999 8666 84433 55566622255 4447777 22335556669. 4666 8666 727774447777.

47777888 995559888 4555 47777888 44999988 666555997 : 8555444888477744488866888648833369!!

I could instantly recognize it being numbers used to type with old mobiles (yes, I'm that old). So it's called multitap and had some decrypters available online, but I decided to brush up my JS knowledge and do it myself.

var encryptedText=prompt("Insert the text to decrypt here.");
var keymap = [];

keymap[2]="a";
keymap[22]="b";
keymap[222]="c";

keymap[3]="d";
keymap[33]="e";
keymap[333]="f";

keymap[4]="g";
keymap[44]="h";
keymap[444]="i";

keymap[5]="j";
keymap[55]="k";
keymap[555]="l";

keymap[6]="m";
keymap[66]="n";
keymap[666]="o";

keymap[7]="p";
keymap[77]="q";
keymap[777]="r";
keymap[7777]="s";

keymap[8]="t";
keymap[88]="u";
keymap[888]="v";

keymap[9]="w";
keymap[99]="x";
keymap[999]="y";
keymap[9999]="z";

keymap[100]=" ";
keymap[101]="\r\n";
keymap[123]=",";
keymap[234]=":";
keymap[345]="!";
keymap[456]=".";
keymap[567]=";";
keymap[678]="?";
keymap[789]="-";


function decryptMobile(encrypted)
{
	toArr=encrypted.split(" ");
	var matched="";
	var numStr = "";
	for(a=0;a<toArr.length;a++)
	{	
		let regXp=/2{1,}|3{1,}|4{1,}|5{1,}|6{1,}|7{1,}|8{1,}|9{1,}|\.|,|:|!|;|\?|-/g;
		matched+=(toArr[a].match(regXp))+',100,';
	}
	
	for(var b=0;b<matched.length-1; b++)
	{
		if(matched[b].includes(' '))
		{
			matched[b].replace(' ','100');
		}
		
		if(matched[b]==',' && matched[b-1]==',' && matched[b+1]==',')
		{
			var add="123";
			var newMatched=matched.substring(0,b) + add + matched.substring(b,matched.length+add.length);
			matched=newMatched;
		}
		
		if(matched[b].includes(':'))
		{
			matched[b].replace(':','234');
		}
		
		if(matched[b].includes('!'))
		{
			matched[b].replace('!','345');
		}
		
		if(matched[b].includes('.'))
		{
			matched[b].replace('.','456');
		}
		
		if(matched[b].includes(';'))
		{
			matched[b].replace(';','567');
		}
		
		if(matched[b].includes('?'))
		{ 
			matched[b].replace('?','678');
		}
		
		if(matched[b].includes('-'))
		{
			matched[b].replace('-','789');
		}
		document.write(matched[b]);
		numStr+=matched[b];
	}
	
	var numArr=numStr.split(",");
	for(c=0; c<numArr.length-1; c++)
	{
		if(keymap[numArr[c]])
		{
			document.write(keymap[numArr[c]]);
		}
		else
		{
			document.write(numArr[c]);
		}
	}
}

decryptMobile(encryptedText);

Now when decrypted, you'll get:

if you are reading the cipher, you are okay. your share of the heist is in your house. the key to the lock is below. go to paris.gsv xlwv gl gsv hzu olxp : tlivgrivnvmgufmw!!

Took me ages, but finally stumbled upon atbash-cipher. So tried decoding with Cryptii and it instalty gave me the ciphertext alphabet: zyxwvutsrqponmlkjihgfedcba

From there we had the answer:

the code to the saf lock goretirementfund!!

And some retard decided, that it's good to say on the HTB's form that the format is HTB{s0m3_t3xt} so took me a while to realise, that the flag is all in caps:

HTB{GORETIREMENTFUND!!}