Age, Bank Account and Phone Number problem

I moved to Tokyo two weeks ago from Kuwait and have finally gotten around to going to get a phone number, I went to Softbank near Akihabara Station and they refused to make a contract with me because I am 19 years old (under 20) so they transferred me to Line Mobile and it was going well until the last step, in which I was supposed to pay for my SIM card plan, my phone is already unlocked (Galaxy S7 edge) so I didn't need to purchase a phone, I have a prepaid VISA card and a Debit VISA card, both were rejected, they asked if I had a Japanese bank account, I told them I needed a number to get a bank account, they suggested I ask a friend to use their credit card to pay while I get the bank account, problem is I've only been here for 2 weeks and do not have any friends who are close enough for me to ask such a thing of them, they told me to wait until next year to make a contract with Softbank, I told them it would be the same problem then, no bank account, no number/ no number, no bank account. They also refuse cash payments so there really was no way out of it, I even asked if I could transfer the payment online using my prepaid but they said it had to go through the machine. Where do I go from now?

My experience a few years ago, just got here as a student, got my residence card and bank account but no cash card yet, the bank said will send later.

Went to Docomo and got rejected because I didnt have the cash card yet. Was told I could pay with credit card, which I didnt have, and then they suggested to borrow a friend which is similar to what you experienced and frankly not a useful advice lol
In the end I waited for my cash card to arrive.

The order of things we need to do is below I believe
1 Residence card
2 Bank account and cash card
3 Phone

So either,
1 Prioritize making bank account first
Go back to the bank you went with someone from university or work etc
If it still doesnt work, go to a different bank, since if I remember correctly I applied to JP post bank only with phone number of my home country

2 Prioritize getting a phone, meaning search for someone with a card and promise to change payment method ASAP

are you here as tourist or student?.if you are student then look for smbc bank around you open account with them or post office bank.
you can use your school number ,hotel number as your contact line when filling up forms.
then try other new network like ymobile .. look for them . i think they can easily register line for you.

Go to Softbank and get a prepaid phone.

I used a skype number for my bank account.
Its a 050 number (instead of 080/090). You have that for a year.

You can also make a 03 number with SONETEL.COM (have a local number in any country. Its paid by a per month basic. ITs actually a forwarding service. But its not like you need to use the forwarding service. just write your kuwait number to forward to or leave it blank.
Its only for putting a number on your bank account application.

When you have your softbank

Sorry, my message somehow got submitted when I hit space. Anyway:

When you have your Softbank number, go to the bank and make the phone number change on your account.

I have already tried with Softbank but I can't make a contract with them, I am 19 years old and their minimum for contracts is 20, if I were 20 this wouldn't really be a problem because softbank accepts cash payments unlike Line Mobile. I have also gone to Line at bicqlo and attempted there, it also didn't work out, I'm having my roommate come with to try and help but if that doesn't work out I'd have to try with the bank account more.

Softbank prepaid phone does not require a contract and does not require a credit card.