Welcome to Vodafone Community
You would need to check on your home countries Vodafone top up options page to see what's available @Mina66iran
There may be an online option or maybe PayPal option or ask someone in your home country to buy a top up voucher and they send you that voucher top up code. Or look in your myvodafone app or see if there's a Vodafone number you can call to get a top up sorted.
Current Phone >
Samsung Z Fold³ 5G.
Previous Phone >
Samsung Note 20 Ultra 5G - SM9860.
Follow this link and top up online here: Vodafone Hungary Top up
If you are staying in the UK, you would find it a lot cheaper if you had a Vodafone UK PAYG SIM card. You can order a free SIM and see the bundles available here: Vodafone PAYG Alternatively, just pop into a store and providing the phone you are using is unlocked to all networks, the staff will get you activated on the UK network.