<div class="radikalwp-form-phone"><span class="radikalwp-form-phone-prefix" dir="ltr">+98<//span><input class="radikalwp-form-phone-input" type="tel" dir="ltr" placeholder="9123456789" aria-label="شماره موبایل"><//div>

.radikalwp-form-phone {
  display: flex;
  align-items: stretch;
  max-width: 300px;
  background: #fff;
  border: 1.5px solid #e2e8f0;
  border-radius: 12px;
  overflow: hidden;
  transition: border-color .25s ease, box-shadow .25s ease;
}
.radikalwp-form-phone:focus-within {
  border-color: #6366f1;
  box-shadow: 0 0 0 4px rgba(99, 102, 241, .14);
}
.radikalwp-form-phone-prefix {
  display: flex;
  align-items: center;
  padding: 0 14px;
  font-size: 13.5px;
  font-weight: 700;
  color: #4f46e5;
  background: #eef2ff;
  border-left: 1.5px solid #e2e8f0;
}
.radikalwp-form-phone-input {
  flex: 1;
  min-width: 0;
  padding: 13px 14px;
  font-family: inherit;
  font-size: 14px;
  color: #1e293b;
  text-align: left;
  border: none;
  outline: none;
}
.radikalwp-form-phone-input::placeholder { color: #cbd5e1; }