Your concern while waiting for a call when his phone is off is understandable, and it is good that you bring it to the Lord in prayer.
Jesus taught very directly about worry, that it has no value and adds nothing. Worry and faith cannot live together in the heart at the same time. When we worry it shows our faith is small, and when we trust God fully worry loses its place. He pointed to the lilies of the field and the way God clothes them, and to the birds He feeds, to remind us that our Father knows what we need. He said not to be anxious about tomorrow, because tomorrow will have its own concerns, and today has enough to entrust to Him. Your waiting and wondering about tomorrow, about when the phone will be on again and when he will call, is the very kind of care Jesus invites you to release into God's hands.
Prayer itself rests on relationship. Jesus taught us to pray by saying Our Father, and that opening word matters more than anything else. If He is not your Father through faith in Jesus Christ, prayer has no foundation. But when you have received Christ, you are not brought into a cold legal arrangement where you try to keep rules to stay accepted. You are adopted as a child of God, and His Spirit bears witness with your spirit that you are His child. That adoption brings a close and tender relationship where you can speak to Him as your Father, even as a dear father you love and trust. He does not want ritual words from you, He wants a living and loving fellowship, and He wants you to know how much He loves you.
That is why your most important need is not for a phone to be recharged at a certain moment, but for that loving relationship with God to be first and deepest. When that relationship is right, every other relationship can be seen more clearly. Scripture calls us to seek first His kingdom and His righteousness, trusting that He will care for the rest. He is the great God who made the heavens, and yet He bends to listen to your small concerns because you are His child.
So instead of letting anxiety grow while you watch the phone, bring your heart to your Father and rest in His care. Ask Him to give you peace that goes beyond circumstances, to grow your faith, and to guide your life and your relationships according to His will and His Word. If this is a friendship or a relationship with a man, place it fully before the Lord and ask Him to lead it in purity and truth, according to His design for marriage as a lifelong covenant between one man and one woman, where intimacy and life together belong. Ask Him to help you both to honor Him above all.
May the Lord quiet your worry today and draw you closer to Himself. May you know His presence as Father, know that you are His child through Jesus, and learn to trust Him with both today and tomorrow. I pray He will fill your heart with His peace as you wait on Him, and that you will find your deepest comfort not in a call you receive, but in the love of the Father who never stops caring for you. In Jesus name, amen.