Your website is asking for a mobile number though. Are you not going to ask us to verify our registration through OTP? If not, won't that be an issue in the future (providing false number)? Can you not make that part optional instead?
In case you provide wrong/false phone number, I think it wont make any effect to your account because so far I do not see the important use of this phone number except for marketing purpose by WA message.
Imagining for the worst case when we need to verify phone number for something, I'm sure there will be a way to change the wrong/false phone number because there is other case when someone may not be able to access his phone number.
If you do not want to provide your real/main phone number, simply use your secondary number.
Bttzed03 is from the Philippines and in the registration table, there's no Philippines in the country selection, hence, there's no phone number format also for the Philippines. I believe he only asked if he can provide a false information just to be able to access the site.
Currently, with the BK8 they didn't support the PH country for me as a user looks like you need to put a false information just to create an account to them and looks like a mandatory KYC better if they made a kyc option for their users after creating an account not just already putted the information upon registration.
They cater both fiat and cryptocurrency gambling, and AFAIK, all fiat gambling sites require KYC in order for their gamblers to play the site. Here, you can use false information and you can enter in the casino, but your account might be at risk of getting banned especially if you are already gambling with decent money.
Just understand the risk, if you are still willing to go, bear with the outcome then.
